Case studies | AQA A-Level Psychology Revision

For 7182 specification, first teach in September 2025

AQA A-Level Psychology | Free Revision Notes

Estimated study time: 50 minutes

These Case studies A-Level Psychology revision notes explain how psychologists conduct detailed investigations of an individual, group, institution or event. You will examine how evidence can be collected from several sources, why case studies are useful for unusual or complex cases, and why their findings may be difficult to generalise. Case studies may combine structured and unstructured conversations, naturalistic or controlled behavioural recording and coding of documents or transcripts.

Learning Objectives 🎯

By the end of this revision page, you should be able to:

• Define the case study method.

• Explain how case studies are designed and conducted.

• Identify the different sources of evidence that a case study may use.

• Explain why case studies can provide detailed information.

• Evaluate the strengths and limitations of case studies.

• Explain why case study findings may have limited generalisability.

• Apply methodological evaluation to an unfamiliar case study.

• Suggest ways of improving the credibility of case study evidence.

Revision Notes 📚

Case studies A-Level Psychology revision overview

A case study is an in-depth investigation of a single individual, small group, institution, community or event.

The researcher aims to develop a detailed understanding of the case rather than collect a small amount of information from a large sample.

A case study may focus on:

• One person.

• A family.

• A small social group.

• A school.

• A workplace.

• A community.

• A particular event.

• An unusual psychological condition.

• A person’s development or recovery over time.

The general process is:

Select a case → collect detailed evidence → combine information from different sources → identify patterns → develop conclusions about the case

Specification boundary

The AQA specification names case studies as a required research method but does not prescribe particular named cases.

This page therefore focuses on:

• The defining features of the method.

• How detailed evidence may be collected.

• Methodological strengths and limitations.

• The generalisability of findings.

No named psychological case is required to understand the research-method principles covered here.

What makes an investigation a case study?

A case study is defined by the depth and focus of the investigation.

It usually examines:

• A limited number of cases.

• A large amount of information about each case.

• The case within its social, personal or historical context.

• Several aspects of the case rather than one isolated score.

For example, a psychologist investigating one student’s experience of severe examination anxiety might collect information about:

• The student’s reported thoughts and feelings.

• Behaviour before and during assessments.

• Attendance records.

• Previous examination experiences.

• Family and school circumstances.

• Changes across the academic year.

• Responses to support.

The purpose is to build a detailed account of the case.

A case study is an overall research strategy

A case study is not one single data-collection technique.

It may contain several techniques, including:

• Interviews.

• Questionnaires.

• Observations.

• Psychological tests.

• Diaries.

• Personal documents.

• Institutional records.

• Audio or video recordings.

• Content analysis.

For example, a researcher studying one school could:

1. Interview teachers.

2. Give pupils questionnaires.

3. Observe lessons.

4. Examine attendance records.

5. Analyse school documents.

The overall investigation is a case study because all the evidence is used to understand one particular school in depth.

Case studies and interviews

Case studies are sometimes confused with interviews because many case studies include detailed conversations.

However:

• An interview is a technique for asking questions.

• A case study is the overall detailed investigation.

A case study may include:

• One interview.

• Several interviews.

• No interviews at all.

The strengths and limitations of questioning participants are covered through structured and unstructured self-report methods.

Case studies and observations

A case study may include observation of the case in:

• An ordinary setting.

• A controlled situation.

• A workplace.

• A classroom.

• A family environment.

• A clinical or research setting.

The observation produces one source of evidence within the wider case study.

Review the relevant distinctions through naturalistic, controlled, covert, overt, participant and non-participant methods.

Case studies and content analysis

Researchers may analyse material associated with the case.

This could include:

• Diaries.

• Letters.

• Interview transcripts.

• Medical records.

• School reports.

• Meeting notes.

• Social-media posts.

• Video recordings.

The researcher may develop categories or themes to organise this material.

The systematic analysis of communication is covered in coding and interpreting communication.

Case studies and experiments

A case study is not automatically an experiment.

An experiment requires:

• Manipulation of an independent variable.

• Measurement of a dependent variable.

• Comparison between conditions.

A case study may simply investigate a person or group without manipulating anything.

For example:

A psychologist studies one individual’s language difficulties using interviews, tests and observations.

This is a case study but not necessarily an experiment.

A researcher could carry out a small experiment within a case study, but the two methods should still be identified separately.

Case studies and correlations

A case study may contain several numerical measures, but this does not automatically make it a correlation.

A correlation requires:

• Two measured co-variables.

• Paired scores.

• Analysis of their relationship.

A case study might examine whether two measures change together within one case, but the overall method remains a detailed investigation of that case.

The analysis of paired variables is covered in relationships between co-variables.

Types of cases investigated

An individual case

A psychologist may study one individual in detail.

This can be useful when the person has:

• An unusual experience.

• A rare pattern of behaviour.

• An uncommon difficulty.

• A particular form of brain damage.

• An exceptional ability.

• Access to information that is difficult to obtain elsewhere.

The researcher may investigate both the person’s current behaviour and their earlier history.

A small group

A case study can investigate a small group whose members share a particular experience.

For example:

• A family.

• A team.

• A support group.

• A group affected by the same event.

• A small class.

• Workers within one department.

The group is examined as a specific case rather than treated as a large representative sample.

An institution

A psychologist may investigate an organisation such as:

• A school.

• A hospital.

• A workplace.

• A care setting.

• A community organisation.

The researcher may explore:

• Relationships.

• Organisational routines.

• Attitudes.

• Behaviour.

• Communication.

• Changes over time.

Different members of the institution may provide different perspectives.

An event or situation

A case study may focus on a particular event.

For example:

• A major organisational change.

• A school introducing a new system.

• A community responding to an unusual event.

• The development of a specific conflict.

• A group completing a long-term project.

The researcher investigates the event in its context rather than isolating a single variable.

An unusual case

Case studies are particularly useful when the case is rare.

A researcher may not be able to recruit a large sample because:

• Few people have the relevant characteristic.

• The event occurs infrequently.

• The situation cannot be recreated.

• Suitable cases are difficult to access.

• Deliberately producing the condition would be unethical.

A detailed investigation may therefore provide evidence that could not be obtained through a large experiment.

A typical case

Case studies do not have to focus on unusual people or events.

A researcher might deliberately investigate a case considered typical of a wider category.

For example:

• An ordinary school.

• A typical family business.

• A routine workplace team.

However, one case judged to be typical may still differ from other apparently similar cases.

The decision that a case is typical must therefore be justified rather than assumed.

Designing a case study

Begin with a clear aim

The researcher should state exactly what the case study will investigate.

For example:

To investigate the experiences of one student returning to education after a five-year absence.

A clear aim helps determine:

• Which case should be selected.

• Which information is relevant.

• Which methods should be used.

• How long the investigation should last.

• How the evidence will be analysed.

The construction of research aims is developed in Aims and hypotheses.

Define the case

The researcher needs clear boundaries.

They should decide:

• Who or what forms the case.

• Which people will provide information.

• Which period will be investigated.

• Which settings will be included.

• Which records may be accessed.

• Which questions are relevant.

For an institutional case study, the researcher might define the case as:

One sixth-form college during the first academic year after a timetable change.

Without clear boundaries, the investigation may expand until it becomes unmanageable.

Select the case appropriately

The case should be selected because it can address the research aim.

A case might be chosen because it is:

• Unusual.

• Informative.

• Accessible.

• Typical of a category.

• Affected by a particular event.

• Available for long-term investigation.

Researchers should explain why the case is suitable.

Choosing a convenient case does not automatically mean it is representative or particularly informative.

Decide which evidence is needed

Researchers may use both quantitative and qualitative data.

Quantitative evidence

This could include:

• Test scores.

• Frequencies.

• Rating-scale responses.

• Attendance totals.

• Performance measures.

• Numerical records.

Qualitative evidence

This could include:

• Interview accounts.

• Personal descriptions.

• Observational notes.

• Diaries.

• Documents.

• Recorded conversations.

The differences between these forms of evidence are explored in Quantitative and qualitative data.

Use more than one source

A detailed case study often combines several sources.

For example:

Source	Information produced
Interview with the individual	Personal experiences and explanations
Interview with a family member	An alternative perspective
Observation	Evidence of behaviour in a particular setting
Psychological test	A standardised performance score
Diary	Experiences recorded across time
School or workplace records	Existing evidence about attendance or performance
Questionnaire	Standardised self-report responses

Combining evidence may produce a fuller understanding of the case.

Primary and secondary data

A case study may include primary data collected specifically for the investigation.

Examples include:

• Research interviews.

• New questionnaires.

• Direct observations.

• Tests administered by the researcher.

It may also use secondary data that already existed.

Examples include:

• Earlier records.

• Personal documents.

• Archived reports.

• Existing recordings.

The difference is covered in researcher-collected and existing evidence.

Plan the period of investigation

A case study may examine the case:

• At one point in time.

• Across several sessions.

• Over months or years.

• Before and after a significant event.

Studying a case over time may reveal:

• Development.

• Recovery.

• Stability.

• Change.

• Responses to new circumstances.

However, longer investigations require greater time and may be affected by participant withdrawal or changing circumstances.

Plan how evidence will be recorded

The researcher should decide whether evidence will be recorded through:

• Written notes.

• Audio recordings.

• Video recordings.

• Test scores.

• Observation schedules.

• Interview transcripts.

• Coding frames.

• Secure digital records.

The method must preserve enough detail for later analysis while protecting confidentiality.

Pilot research materials

Parts of the case study may be piloted.

For example, researchers might test:

• Interview questions.

• Questionnaire wording.

• Observation categories.

• Recording procedures.

• Coding systems.

A pilot can identify:

• Ambiguous questions.

• Missing categories.

• Practical difficulties.

• Recording failures.

• Procedures that take too long.

This process is covered in testing and improving research procedures.

Collecting detailed evidence

Interviews within case studies

Interviews can provide information about:

• Thoughts.

• Feelings.

• Memories.

• Motivations.

• Interpretations.

• Personal history.

Structured interviews allow comparison and replication.

Unstructured interviews allow the researcher to:

• Explore unexpected topics.

• Ask for clarification.

• Follow the participant’s account.

• Collect greater detail.

However, interview evidence may be affected by:

• Social desirability.

• Memory errors.

• Demand characteristics.

• Interviewer effects.

• Leading questions.

Questionnaires within case studies

Questionnaires may collect:

• Rating scores.

• Frequency estimates.

• Attitudes.

• Experiences.

• Open written accounts.

They can provide a standardised record that can be repeated over time.

However, a questionnaire may provide less depth than an interview and may not allow immediate clarification.

Review item design through open and closed self-report questions.

Observations within case studies

Observations may reveal behaviour that participants:

• Do not notice.

• Cannot remember.

• Are unwilling to report.

• Describe inaccurately.

For example, a researcher studying one classroom might observe:

• Teacher-pupil interaction.

• Pupil participation.

• Responses to feedback.

• Group behaviour.

Observation may be affected by:

• Observer bias.

• Behavioural reactivity.

• Lack of control.

• Difficulty recording complex behaviour.

Psychological or behavioural tests

Tests may provide standardised measurements.

For example, a case study could include repeated measures of:

• Memory.

• Attention.

• Language.

• Problem solving.

• Reaction time.

Standardised tests may make change easier to track.

However, performance may be influenced by:

• Practice.

• Fatigue.

• Motivation.

• Test anxiety.

• Understanding of the instructions.

• The validity of the test.

Records and documents

Existing records may provide information covering a longer period than the researcher could observe directly.

They might include:

• School reports.

• Attendance records.

• Workplace records.

• Earlier assessments.

• Diaries.

• Letters.

• Meeting notes.

However, researchers should consider:

• Why the record was created.

• Whether it is complete.

• Whether it is accurate.

• Whether different people recorded information consistently.

• Whether permission exists to use it.

Information from other people

Researchers may collect information from:

• Relatives.

• Friends.

• Teachers.

• Colleagues.

• Professionals.

• Other members of a group.

These accounts may provide useful alternative perspectives.

However, they may also be affected by:

• Personal relationships.

• Limited knowledge.

• Memory errors.

• Conflict.

• Desire to protect or criticise the case.

• Different interpretations of events.

The researcher should not assume that an external account is automatically objective.

Triangulation

What is triangulation?

Triangulation involves comparing evidence obtained from different methods, sources or researchers.

For example, a case study might compare:

• What the participant says in an interview.

• What is recorded in a diary.

• What the researcher observes.

• What appears in institutional records.

If the sources support a similar conclusion, confidence in the interpretation may increase.

Method triangulation

Method triangulation involves using more than one research technique.

For example:

• Interview.

• Observation.

• Questionnaire.

• Test.

Each method has different strengths and limitations.

Agreement across methods reduces the likelihood that the finding is caused entirely by one method’s weakness.

Source triangulation

Source triangulation involves obtaining information from different people or records.

For example:

• The individual.

• A relative.

• A teacher.

• A school record.

The sources may agree, provide complementary information or contradict one another.

Contradiction should be investigated rather than ignored.

Researcher triangulation

More than one researcher may examine the evidence.

This can reduce the dependence of conclusions on one person’s interpretation.

Researchers might:

• Code transcripts independently.

• Compare observations.

• Review documents separately.

• Discuss alternative explanations.

Agreement can support reliability, although several researchers may still share similar assumptions.

Limits of triangulation

Triangulation does not guarantee that a conclusion is correct.

Several sources may agree because:

• They rely on the same original information.

• The people involved influence one another.

• The researchers use the same assumptions.

• Records copy earlier records.

• Similar biases affect each method.

Triangulation strengthens a conclusion only when the sources provide meaningfully different forms of evidence.

Analysing case study evidence

Organising large amounts of information

Case studies may produce extensive data.

Researchers need a clear system for organising:

• Interview transcripts.

• Notes.

• Scores.

• Documents.

• Timelines.

• Observations.

• Recordings.

Without systematic organisation, important evidence may be:

• Missed.

• Repeated unnecessarily.

• Taken out of context.

• Selected according to researcher expectations.

Constructing a timeline

A timeline may help researchers understand:

• The order of events.

• Changes in behaviour.

• Possible relationships between experiences.

• When difficulties began.

• When improvement occurred.

However, events occurring before the investigation may depend on retrospective memories or incomplete records.

Coding qualitative evidence

Interview transcripts, documents and observational notes may be analysed using coding categories.

Researchers might identify themes such as:

• Social support.

• Anxiety.

• Avoidance.

• Conflict.

• Coping.

• Improvement.

Categories should be:

• Relevant to the aim.

• Clearly defined.

• Applied consistently.

• Supported by examples.

The process is covered in Content analysis.

Comparing evidence across sources

Researchers should examine whether sources:

• Agree.

• Disagree.

• Address different parts of the case.

• Reflect different time periods.

• Were produced for different purposes.

For example, a student may report being highly engaged in school, while attendance records show frequent absence.

The researcher should consider several possible explanations rather than automatically deciding that one source is correct.

Avoiding selective evidence

A researcher may be tempted to focus on evidence that supports their preferred explanation.

This is a form of researcher bias.

To reduce it, the report should include:

• Evidence supporting the conclusion.

• Evidence that does not fit.

• Alternative explanations.

• Limitations of each source.

• Clear links between evidence and interpretation.

Strengths of case studies

Strength: detailed information

A major strength is the depth of evidence produced.

A case study may investigate:

• Behaviour.

• Thoughts.

• Feelings.

• Relationships.

• Personal history.

• Environmental influences.

• Change over time.

This can provide a more complete account than one test score or questionnaire response.

Strength: holistic understanding

A detailed investigation considers several aspects of the case together.

For example, a student’s academic performance may be examined alongside:

• Motivation.

• Attendance.

• Family circumstances.

• Health.

• Friendships.

• Teaching.

• Revision behaviour.

This may produce a more realistic explanation than studying one variable in isolation.

However, greater complexity can make it difficult to determine which factor is most influential.

Strength: unusual cases can be investigated

A case study may be the only practical method when:

• The characteristic is rare.

• The event cannot be recreated.

• Few suitable participants exist.

• Experimental manipulation would be unethical.

• The person has a unique history.

The method allows psychologists to learn from evidence that would otherwise be inaccessible.

Strength: generates new hypotheses

A detailed case may reveal:

• An unexpected behaviour.

• A new relationship.

• A possible explanation.

• A weakness in an existing theory.

• A question for future research.

Researchers can then investigate the idea using:

• Larger samples.

• Experiments.

• Correlations.

• Additional case studies.

A case study is often valuable as the beginning of an investigation rather than its final answer.

Strength: may challenge an existing claim

A carefully documented case may show that an established explanation does not apply in every situation.

For example, if a theory predicts that a particular outcome must always occur, one reliable case without that outcome may require the theory to be reconsidered.

However, the case must be:

• Accurately documented.

• Relevant to the claim.

• Interpreted cautiously.

• Supported by valid evidence.

Strength: several methods can be combined

Using several methods allows researchers to collect:

• Objective scores.

• Personal accounts.

• Behavioural evidence.

• Historical information.

Agreement across sources may increase confidence in the conclusions.

This can strengthen whether the evidence measures what it claims to measure.

Strength: high ecological validity may be possible

Case studies often investigate people within their real circumstances.

The researcher may study:

• Genuine relationships.

• Real-life decisions.

• Existing routines.

• Meaningful experiences.

• Natural changes across time.

The findings may therefore reflect the complexity of everyday life more accurately than an artificial task.

However, this depends on the exact methods used.

A case study based entirely on controlled testing may have lower ecological validity.

Strength: change can be tracked over time

Repeated investigation may show:

• Development.

• Recovery.

• Decline.

• Responses to support.

• Changes following an event.

This can provide information that would be missed by a single assessment.

However, change across time does not automatically reveal its cause.

Limitations of case studies

Limitation: low generalisability

The central limitation is that findings from one case or a small number of cases may not apply to a wider population.

The case may be unusual in terms of:

• Age.

• Experience.

• Biology.

• Personality.

• Social environment.

• Previous support.

• Education.

• Culture.

A result may therefore explain the selected case without explaining other people.

Limitation: the case may be unique

An unusual case is valuable because it is rare, but that rarity also makes it difficult to generalise.

For example, a person may have:

• An uncommon combination of experiences.

• A distinctive pattern of damage.

• Unusual personal circumstances.

• Access to exceptional support.

The researcher cannot assume that another person with one similar characteristic would show the same outcome.

Limitation: no representative sample

Many case studies do not use a representative sample.

The case may be selected because it is:

• Available.

• Dramatic.

• unusual.

• Willing to participate.

• Well documented.

These features may distinguish it from the wider population.

The relationship between samples and wider populations is developed in Populations and samples.

Limitation: difficulty replicating

The exact case cannot usually be recreated.

Another researcher cannot reproduce:

• The person’s life history.

• The same injury or event.

• The same social relationships.

• The same environmental circumstances.

• The same development across time.

Researchers may repeat the methods, but they cannot repeat the original case itself.

This limits consistency of findings across repeated investigations.

Limitation: researcher bias

Case study evidence often requires interpretation.

Researchers decide:

• Which questions to ask.

• Which records to examine.

• Which events are important.

• Which quotations to include.

• How different sources are combined.

• Which explanation best fits the evidence.

Their expectations may influence the final account.

The greater the amount of complex qualitative evidence, the more opportunity there may be for selective interpretation.

Limitation: participant reactivity

The person being studied may alter their behaviour because they know they are receiving detailed attention.

They may:

• Try to support the researcher.

• Present themselves favourably.

• Become self-conscious.

• Guess the aim.

• Change what they report over time.

This may reduce validity.

The wider issue is covered in Demand characteristics and investigator effects.

Limitation: retrospective evidence

Some case studies investigate events from the past.

Researchers may rely on:

• Memories.

• Old documents.

• Reports from relatives.

• Incomplete records.

Memories can be:

• Inaccurate.

• Reconstructed.

• Influenced by later experiences.

• Affected by current beliefs.

Historical evidence may also have been created for a different purpose.

Limitation: cannot usually establish cause and effect

A case study may identify several possible influences, but these are not normally manipulated or controlled experimentally.

Suppose a person improves after receiving support.

The improvement could be related to:

• The support.

• Time passing.

• Practice.

• Medication.

• A change in circumstances.

• Increased motivation.

• Several interacting factors.

The case study can describe the sequence but may not establish which factor caused the outcome.

Limitation: large amounts of data

Detailed investigation may produce more information than researchers can analyse easily.

This can create problems involving:

• Organisation.

• Transcription.

• Coding.

• Interpretation.

• Secure storage.

• Selection of evidence for the final report.

The researcher must reduce the evidence to a manageable account without oversimplifying it.

Limitation: time and cost

Case studies may require:

• Repeated meetings.

• Travel.

• Long interviews.

• Extensive observation.

• Transcription.

• Record analysis.

• Specialist testing.

• Long-term contact.

This limits the number of cases that can be investigated.

Limitation: access may be difficult

Researchers may need permission from:

• The individual.

• Relatives.

• Schools.

• Workplaces.

• Healthcare services.

• Other organisations.

Access may be restricted because the material is:

• Private.

• Sensitive.

• Legally protected.

• Potentially distressing.

• Identifiable.

Generalisability of case study findings

What is generalisability?

Generalisability is the extent to which findings can be applied beyond the people, setting or circumstances studied.

For a case study, researchers should ask:

• Does this finding apply only to the selected case?

• Might it apply to similar cases?

• Is there evidence that it applies to a wider population?

• Which features of the case may have influenced the result?

• Has the finding been supported by other investigations?

Why sample size matters

A single person or group cannot represent the full variety within a population.

For example, one student cannot represent every:

• A-Level student.

• Student experiencing anxiety.

• Student in the same school.

• Student of the same age.

People differ in many relevant ways.

A larger sample generally captures more variation, although size alone does not guarantee representativeness.

Why unusual cases are especially difficult to generalise

A case may have been selected because it is exceptional.

This produces a tension:

• Its unusual nature makes it interesting.

• Its unusual nature makes it unrepresentative.

Researchers should avoid moving directly from:

This happened in one rare case.

to:

This is how people generally behave.

Generalising to similar cases

A cautious researcher might consider whether the finding applies to cases sharing important characteristics.

For example:

• Similar age.

• Similar experience.

• Similar environment.

• Similar type of difficulty.

• Similar level of support.

Even then, the finding should be treated as a possibility rather than a certainty.

Generalising principles rather than statistics

A case study may suggest a process or principle that can be investigated elsewhere.

For example, it might suggest that:

• Social support is relevant.

• A particular strategy may help.

• An existing explanation is incomplete.

• An unexpected ability is possible.

The researcher can then test this principle using further evidence.

This is more defensible than claiming that the frequency found in one case represents the whole population.

Replication across several cases

Confidence may increase if:

• Several independent case studies show a similar pattern.

• Cases differ in some background features.

• Different researchers obtain similar findings.

• Different methods support the same interpretation.

• Later research using larger samples reaches a compatible conclusion.

Repeated support does not transform case studies into a representative experiment, but it reduces dependence on one unique case.

One case can demonstrate possibility

A well-documented case may show that something can occur.

For example, it may demonstrate that:

• A particular behaviour is possible.

• An expected outcome is not inevitable.

• A theory has an exception.

• A rare pattern exists.

This is different from showing:

• How common the pattern is.

• Whether it applies to most people.

• What caused it.

• Whether it would occur under other circumstances.

Avoiding overgeneralisation

A suitable conclusion might state:

The findings provide a detailed explanation of this participant’s experience and may suggest factors worth investigating in similar cases.

An unsuitable conclusion would state:

The findings prove that all people in this situation will respond in the same way.

The second conclusion goes beyond the evidence.

Evaluating validity in case studies

Potential for high validity

A case study may have high validity because it can:

• Collect detailed evidence.

• Clarify participant meaning.

• Examine the case in context.

• Compare several sources.

• Track change across time.

• Investigate real behaviour.

The researcher may gain a more accurate understanding than would be possible through a brief questionnaire.

Threats to validity

Validity may be reduced by:

• Researcher interpretation.

• Participant demand characteristics.

• Socially desirable answers.

• Inaccurate memories.

• Incomplete records.

• Leading questions.

• Selective reporting.

• Unrepresentative testing situations.

Detail should not be confused automatically with accuracy.

A lengthy account may still be biased or mistaken.

Improving validity

Validity may be improved through:

• Triangulation.

• Clear operational definitions.

• Neutral interviewing.

• Direct observation.

• Use of reliable records.

• Consideration of contradictory evidence.

• Repeated assessments.

• Careful separation of evidence and interpretation.

The wider principles are covered in Validity.

Evaluating reliability in case studies

Why reliability may be low

Case studies are difficult to replicate because:

• Cases are unique.

• Procedures may change as new evidence appears.

• Unstructured interviews may be used.

• Qualitative interpretation is involved.

• Circumstances change across time.

Another researcher may investigate the same case and reach a different conclusion.

Improving reliability

Researchers can improve consistency by:

• Standardising tests.

• Using an interview schedule where appropriate.

• Recording procedures clearly.

• Audio or video recording with consent.

• Operationalising coding categories.

• Using more than one researcher.

• Comparing coding decisions.

• Keeping a clear record of how conclusions were reached.

These steps cannot make the case itself repeatable, but they make the investigation more transparent.

Review the broader principles through Reliability.

Ethical issues in case studies

Informed consent

Participants should understand:

• The nature of the investigation.

• The types of information collected.

• How long participation may last.

• Which records may be accessed.

• Whether interviews will be recorded.

• How findings will be reported.

• Their right to withdraw.

In a long case study, consent may need to be confirmed as the investigation develops.

Confidentiality

Confidentiality can be particularly difficult because detailed cases may be recognisable even when names are changed.

Readers may identify the person from:

• Age.

• Occupation.

• Institution.

• Family circumstances.

• Unusual experiences.

• Details of an event.

• Direct quotations.

Researchers should remove or alter unnecessary identifying details while preserving the psychological meaning of the evidence.

Anonymity may be impossible

Complete anonymity may be difficult when:

• The case is already publicly known.

• The characteristics are highly unusual.

• The study concerns one institution.

• People within a community know who participated.

Researchers should not promise anonymity if they cannot provide it.

They should explain realistically how identity will be protected.

Right to withdraw

Participants should be able to:

• Refuse particular questions.

• Pause data collection.

• Withdraw from later sessions.

• Request removal of their data where possible.

Withdrawal may become complicated once:

• Information has been combined with other evidence.

• Findings have been published.

• Anonymous data can no longer be identified.

The limits should be explained clearly.

Protection from harm

Detailed investigation may involve repeated discussion of:

• Trauma.

• Personal relationships.

• Illness.

• Failure.

• Conflict.

• Distressing memories.

Researchers must consider whether repeated questioning could cause:

• Anxiety.

• Embarrassment.

• Emotional distress.

• Damage to relationships.

• Unwanted public attention.

The scientific value of the case study does not remove the responsibility to protect participants.

Information about third parties

Participants may reveal information about people who have not consented to the study.

For example, an interview may describe:

• Family members.

• Friends.

• Teachers.

• Colleagues.

• Professionals.

Researchers must consider how to report this material without identifying or unfairly representing people who are not participants.

Researcher-participant relationship

Long-term case studies may create a close relationship between the researcher and participant.

This can affect:

• Objectivity.

• Expectations.

• Dependence.

• Boundaries.

• The participant’s willingness to withdraw.

Researchers should maintain appropriate professional boundaries.

The broader safeguards are covered in Ethics in psychological research.

Practical issues in case studies

Recruitment

Finding a suitable case may be difficult.

The person or institution must:

• Meet the research criteria.

• Be willing to participate.

• Be accessible.

• Permit relevant records or settings to be examined.

• Remain involved long enough for useful evidence to be collected.

Maintaining participation

Long investigations may experience:

• Participant withdrawal.

• Missed appointments.

• Changes in circumstances.

• Loss of access.

• Fatigue.

• Declining motivation.

Researchers need procedures that minimise burden.

Managing records

Case study evidence must be stored securely and systematically.

Researchers may need to manage:

• Consent forms.

• Audio recordings.

• Video recordings.

• Transcripts.

• Test scores.

• Documents.

• Observation notes.

• Contact information.

Identifying information should be separated from research data where appropriate.

Reporting the case

A case study report should distinguish:

• Direct evidence.

• Participant statements.

• Other people’s accounts.

• Researcher observations.

• Researcher interpretations.

• Alternative explanations.

The conventions used in research reports are developed in Reporting psychological investigations.

Case study compared with other methods

Method	Main focus	How it differs from a case study
Experiment	Effect of an IV on a DV	Prioritises manipulation, control and comparison
Correlation	Relationship between co-variables	Prioritises paired numerical measurements
Observation	Directly observable behaviour	May provide one source of case study evidence
Questionnaire	Written self-report answers	Usually collects a narrower standardised set of responses
Interview	Verbal self-report answers	May be one part of a wider case study
Content analysis	Systematic analysis of communication	May be used to analyse case study records or transcripts
Case study	Detailed investigation of a bounded case	May combine several of the other techniques

Selecting a case study for a research scenario

Scenario: a rare experience

A psychologist has access to one person with an extremely unusual pattern of memory difficulty.

A case study may be suitable because:

• A large sample is unavailable.

• The person can be investigated in depth.

• Several abilities can be assessed.

• Earlier records may be examined.

• Change can be tracked over time.

• The findings may generate new hypotheses.

However:

• The person may not represent others.

• The pattern may reflect a unique history.

• Cause and effect may remain unclear.

• Confidentiality may be difficult.

Scenario: one school undergoing change

A researcher wants to understand how one school responds to a major change in its timetable.

A case study may allow:

• Interviews with staff and pupils.

• Classroom observations.

• Questionnaire ratings.

• Analysis of attendance records.

• Comparison of evidence across the academic year.

The findings may explain the experience of that school but should not be generalised automatically to every school.

Scenario: personal adjustment over time

A psychologist wants to understand how one individual adjusts after moving to a new country.

A case study may collect:

• Repeated interviews.

• Diary entries.

• Social-interaction observations.

• Wellbeing ratings.

• Accounts from family members.

This may provide a rich account of change over time.

However, personal, cultural and social circumstances may make the case highly individual.

A method for evaluating a case study

Step 1: identify the case

State who or what was investigated.

Step 2: identify the evidence collected

Refer to the specific:

• Interviews.

• Observations.

• Tests.

• Documents.

• Records.

Step 3: explain the benefit of depth

State what the researcher can understand that a brief or large-scale method might miss.

Step 4: evaluate data quality

Consider:

• Reliability.

• Validity.

• Researcher bias.

• Participant reactivity.

• Triangulation.

Step 5: evaluate generalisability

Identify the features that make the case different from the wider population.

Step 6: consider causation

Explain whether variables were manipulated or alternative explanations controlled.

Step 7: consider ethics

Apply issues such as:

• Confidentiality.

• Consent.

• Withdrawal.

• Protection from harm.

Writing an effective definition

A strong definition might state:

A case study is an in-depth investigation of an individual, small group, institution or event. Researchers often collect detailed qualitative and quantitative evidence using several techniques, such as interviews, observations, tests and records.

This definition identifies:

• The unit investigated.

• The depth of the investigation.

• The possible use of several methods.

• The forms of evidence collected.

Writing an effective strength paragraph

One strength of a case study is that it can provide detailed information about a complex or unusual case. Researchers may combine interviews, observations, tests and existing records, allowing the case to be understood within its real-life context. Agreement between these sources may increase validity through triangulation. However, the large amount of evidence still requires researcher interpretation, so selective reporting may influence the final conclusion.

Writing an effective limitation paragraph

One limitation of a case study is low generalisability. A case may have a unique personal history, environment or combination of characteristics that is not shared by the wider population. Findings that accurately explain the selected participant may therefore not apply to other people. Further case studies and larger investigations would be needed before drawing a broader conclusion.

Writing an effective generalisability judgement

A developed judgement might state:

The findings cannot be generalised confidently because only one unusually experienced participant was investigated. Their behaviour may have been affected by their personal history and support, rather than the characteristic that interested the researcher. Nevertheless, the case may demonstrate that the behaviour is possible and may generate a hypothesis that can be tested using a larger and more representative sample.

Overall evaluation

Case studies are particularly useful when psychologists need:

• Detailed information.

• Evidence about an unusual case.

• An understanding of behaviour in context.

• Several sources of data.

• Evidence of change over time.

• New hypotheses for future research.

Their main limitations include:

• Low generalisability.

• Difficulty replicating the case.

• Researcher interpretation.

• Participant reactivity.

• Retrospective inaccuracies.

• Limited control.

• Inability to establish cause and effect.

• Practical and ethical demands.

The strongest case studies:

• Define the case clearly.

• Use evidence relevant to the aim.

• Combine independent sources.

• Apply transparent analysis.

• Consider contradictory evidence.

• Protect participants.

• Avoid claims beyond what the case supports.

Key Words 🔑

Key word	Student-friendly definition	How it may be used in an exam
Case study	An in-depth investigation of an individual, small group, institution or event.	Define the method or identify it in a research scenario.
Case	The person, group, organisation or event being investigated.	Identify the focus and boundaries of the investigation.
In-depth investigation	Research that collects extensive information about a limited number of cases.	Explain the defining feature of a case study.
Qualitative data	Detailed descriptive information usually expressed in words.	Identify interview, diary or observational evidence.
Quantitative data	Numerical information that can be counted or measured.	Identify test scores, ratings or frequencies.
Primary data	Evidence collected specifically for the current investigation.	Identify interviews, observations or tests conducted by the researcher.
Secondary data	Evidence that existed before the current investigation.	Identify records, reports or archived documents.
Triangulation	Comparing evidence from different methods, sources or researchers.	Explain how confidence in a case study conclusion may be increased.
Method triangulation	Using more than one data-collection technique.	Explain the combination of interviews, observations and tests.
Source triangulation	Comparing information obtained from different people or records.	Evaluate agreement between evidence sources.
Researcher bias	The researcher’s expectations influencing data collection or interpretation.	Evaluate subjective analysis and selective reporting.
Generalisability	The extent to which findings apply beyond the case studied.	Evaluate evidence from one person or institution.
Population	The wider group to which the researcher may wish to apply the findings.	Explain the limits of conclusions from one case.
Sample	The person or people who actually take part in research.	Compare a case with the wider target population.
Ecological validity	The extent to which evidence represents behaviour in everyday settings.	Evaluate real-life investigation of the case.
Reliability	The consistency of a procedure or finding.	Evaluate replication and coding agreement.
Validity	The extent to which evidence measures or represents what it claims.	Evaluate detail, triangulation and researcher interpretation.
Retrospective data	Information about events that occurred before the research began.	Evaluate memories and historical records.
Longitudinal investigation	Research examining a case across an extended period.	Explain how change or development may be tracked.
Demand characteristics	Cues that lead participants to guess the aim and alter their responses.	Evaluate participant reactivity during detailed investigation.
Confidentiality	Protecting personal information and participants’ identities.	Explain a major ethical issue in case studies.
Informed consent	Agreement to participate based on sufficient information.	Explain ethical procedures before collecting detailed evidence.
Right to withdraw	The right to stop participating or request removal of data.	Explain participant control during a long investigation.
Protection from harm	The responsibility to avoid unnecessary physical or psychological risk.	Evaluate repeated questioning about sensitive experiences.
Replication	Repeating a research procedure to check whether findings are consistent.	Explain why unique cases are difficult to reproduce.

Common Mistakes ⚠️

Mistake: Defining a case study as an interview with one person.

Why this is incorrect:An interview is one possible technique. A case study is the wider in-depth investigation and may use several sources.

How to improve:Refer to detailed evidence collected through interviews, observations, tests or records.

Mistake: Saying case studies can investigate only individuals.

Why this is incorrect:A case may be an individual, group, institution, community or event.

How to improve:Define the method broadly while identifying the particular case in the scenario.

Mistake: Calling every study with one participant a case study.

Why this is incorrect:A brief experiment with one participant may not investigate the case in depth.

How to improve:Look for extensive contextual information and several forms of evidence.

Mistake: Describing a case study as an experimental design.

Why this is incorrect:Case study refers to a research method or strategy, while independent groups, repeated measures and matched pairs describe allocation to experimental conditions.

How to improve:Classify the detailed investigation separately from any design used within it.

Mistake: Saying detailed evidence is automatically valid.

Why this is incorrect:Participants may misremember or respond socially desirably, and researchers may interpret evidence selectively.

How to improve:Evaluate the quality and source of the detail collected.

Mistake: Saying triangulation proves the conclusion.

Why this is incorrect:Different sources may share the same error or rely on the same original information.

How to improve:State that independent agreement may increase confidence rather than guarantee accuracy.

Mistake: Claiming that one case represents the entire population.

Why this is incorrect:The case may have unusual personal, biological, cultural or environmental characteristics.

How to improve:Limit conclusions to the case and identify the need for further evidence.

Mistake: Saying case studies are useless because they cannot be generalised.

Why this is incorrect:They can provide detailed evidence, investigate rare cases and generate hypotheses.

How to improve:Balance limited generalisability against the method’s contribution to psychological understanding.

Mistake: Assuming a rare case shows how common a behaviour is.

Why this is incorrect:A single case may demonstrate possibility but cannot estimate prevalence.

How to improve:Separate evidence that something can occur from evidence about how frequently it occurs.

Mistake: Claiming that change across time proves causation.

Why this is incorrect:Several uncontrolled factors may have changed during the investigation.

How to improve:Consider alternative explanations such as practice, support or environmental change.

Mistake: Saying case studies are easy to replicate because the procedure is described.

Why this is incorrect:The same person, history and circumstances cannot usually be recreated.

How to improve:Distinguish repeating the data-collection procedures from reproducing the case.

Mistake: Ignoring researcher bias.

Why this is incorrect:Researchers select evidence and decide how different sources should be interpreted.

How to improve:Suggest clear procedures, triangulation and consideration of alternative explanations.

Mistake: Assuming changing a participant’s name guarantees anonymity.

Why this is incorrect:A person may remain identifiable from detailed information about their life or circumstances.

How to improve:Remove unnecessary identifying details and be realistic about the limits of anonymity.

Mistake: Giving a generic statement that case studies lack generalisability.

Why this is incomplete:Evaluation should explain which features make the particular case unrepresentative.

How to improve:Refer to the case’s age, history, environment, experience or unusual characteristics.

Mistake: Listing several methods without explaining why they are useful.

Why this is incomplete:The examiner needs to understand how the sources contribute to the investigation.

How to improve:Explain what each method measures and how the evidence can be compared.

Exam-Style Questions ✍️

Question 1

Which one of the following best describes a case study?

A. A statistical analysis of two co-variablesB. An in-depth investigation of an individual, group, institution or eventC. A researcher-manipulated comparison between two conditionsD. A standardised set of written questions given to a large sample

[1 mark]

Question 2

Define the case study method.

[2 marks]

Question 3

Explain why a case study may use more than one data-collection technique.

[3 marks]

Question 4

A psychologist conducts repeated interviews with one student, observes the student during lessons and examines their attendance records.

Explain why this investigation is a case study.

[4 marks]

Question 5

Explain one strength and one limitation of investigating an unusual individual using a case study.

[6 marks]

Question 6

A researcher conducts a detailed case study of one school after it introduces a new timetable.

Explain two sources of evidence the researcher could collect.

[4 marks]

Question 7

A psychologist interviews one participant, examines their diary and obtains information from a family member.

Explain how triangulation could strengthen the investigation.

[4 marks]

Question 8

A researcher concludes that all students returning to education will have the same experience as the one participant in her case study.

Explain why this conclusion may not be justified.

[4 marks]

Question 9

A psychologist publishes a detailed case study of an individual with an unusual psychological difficulty. The participant is given a different name, but their age, workplace and personal history are reported.

Explain one ethical issue raised by this procedure.

[4 marks]

Question 10

Discuss case studies as a psychological research method.

Refer to detailed investigation and the generalisability of findings in your answer.

[8 marks]