All subjects · Psychology · WPS04 Clinical Psychology and Psychological Skills

Research methods review: data, sampling, designs and methods

Edexcel IAL Psychology · WPS04 Clinical Psychology and Psychological Skills

Topic I is synoptic: it draws together research methods from Topics A to H (excluding F and G). This lesson reviews spec 9.1.1 to 9.1.8, with examples from studies across the course. Section C of the paper (20 marks) tests these skills.

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Data, sampling and designs (9.1.1 to 9.1.3)

Concept	Key points	Course example
Qualitative / quantitative	Words and meanings vs numbers	Becker et al. (2002) used both
Primary / secondary	Collected by the researcher vs existing data	Clinical practical uses secondary data
Random sampling	Everyone has an equal chance; unbiased but hard to achieve	Random allocation in RCTs (a different idea: allocation, not selection)
Stratified	Subgroups in proportion to the population	Useful when age or gender matters
Volunteer	Self-selected; may be unrepresentative	Milgram (1963); Ma, Quan and Liu (2014)
Opportunity	Whoever is available; quick but biased	Many student studies
Independent groups	Different people per condition; no order effects but participant variables	Patients vs controls (Suzuki et al.)
Repeated measures	Same people in all conditions; order effects	Before and after therapy
Matched pairs	Pairs matched on key variables	Reichel et al. matched age and education

Hypotheses (9.1.4)

Null: there will be no difference/relationship (any found is due to chance).
Alternate (experimental): there will be a difference/relationship.
Directional (one-tailed): states the direction. Non-directional (two-tailed): does not.
Always fully operationalise the IV and DV: for example, 'Clients will have lower scores on the Beck Depression Inventory after 12 sessions of CBT than before.'

Methods (9.1.5 to 9.1.8)

Questionnaires: open and closed questions, including ranked (Likert) scales; self-report risks social desirability.
Interviews: structured (fixed questions, reliable), semi-structured (core questions plus follow-ups), unstructured (conversation, rich but hard to compare).
Experiments: laboratory (high control, low ecological validity) and field (natural setting, less control); IV manipulated, DV measured. Naturalistic experiments are not required.
Observations: tallying, event and time sampling; covert or overt; participant or non-participant; structured or naturalistic.
Correlations: positive, negative or zero; cannot show cause and effect because of direction and third variables.

Worked example

Write a fully operationalised directional hypothesis for a study testing whether family therapy reduces relapse.

Identify the IV: whether patients receive family therapy plus medication or medication alone.
Identify the DV and how it is measured: the number of patients readmitted to hospital within 12 months.
State the direction.
Hypothesis: 'Fewer patients with schizophrenia who receive family therapy plus medication will be readmitted to hospital within 12 months than patients receiving medication alone.'

Answer: Both variables operationalised, with a direction.

Key idea: Know qualitative/quantitative and primary/secondary data; random, stratified, volunteer and opportunity sampling; three designs; null, alternate, directional and non-directional hypotheses (operationalised); questionnaires, interviews, experiments, observations and correlations, with a course example of each.

Check yourself

A researcher divides a population by age group and selects people from each group in proportion to its size. This is
- random sampling
- opportunity sampling
- volunteer sampling
- stratified sampling
Show answer
stratified sampling. Proportional subgroups = stratified.
Which design avoids order effects but risks participant variables?
- Repeated measures
- Independent groups
- Matched pairs
- A case study
Show answer
Independent groups. Different people in each condition.
A non-directional hypothesis is tested with a
- one-tailed test
- chi-squared test only
- case study
- two-tailed test
Show answer
two-tailed test. No direction predicted: two-tailed.
Which type of interview uses set questions but allows follow-up questions?
- Semi-structured
- Structured
- Unstructured
- Closed questionnaire
Show answer
Semi-structured. Core questions plus flexibility.
Recording behaviour every 30 seconds is an example of
- event sampling
- covert observation
- time sampling
- content analysis
Show answer
time sampling. Time sampling records at fixed intervals.
Explain one weakness of an independent groups design.
Show answer
Different people are in each condition, so individual differences such as age or personality could affect the results instead of the IV.. Participant variables may confound the results.
Write a non-directional hypothesis for a study comparing anxiety ratings (1 to 10) of patients before and after an fMRI scan.
Show answer
There will be a difference in patients' anxiety ratings on a 1 to 10 scale before and after an fMRI scan.. Non-directional: states a difference without saying which way, with operationalised variables.

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Last updated 8 November 2026. Spotted a mistake? Tell us.