How do psychologists design research to test their ideas?
Designing psychological research: aims and hypotheses (including null and alternative), experimental designs, types of experiment, and other research methods such as observations, questionnaires and case studies.
A focused answer to Edexcel GCSE Psychology Topic 11, covering how research is designed: aims and hypotheses (null and alternative), experimental designs, types of experiment, and other methods.
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What this dot point is asking
Edexcel wants you to explain how psychologists design research: writing aims and hypotheses (including null and alternative), choosing experimental designs, knowing the types of experiment, and understanding other methods (observations, questionnaires, interviews and case studies). This is the foundation of Topic 11 (Research methods) and is examined across both papers.
Aims and hypotheses
A good hypothesis is operationalised, meaning it states how the variables are measured (for example "faster mean reaction time, in milliseconds"). Hypotheses can be directional (predicting the direction of the effect, for example "faster") or non-directional (predicting a difference without a direction, for example "different"). Researchers decide between the alternative and null hypothesis after analysing the data.
Experimental designs
Types of experiment and other methods
The type of experiment describes the setting and control.
- Laboratory experiment: in a controlled setting; high control and replicable, but can be artificial (low ecological validity), like Peterson and Peterson.
- Field experiment: in a real-life setting; higher ecological validity, but less control, like Piliavin's subway study.
- Natural experiment: the independent variable occurs naturally (not manipulated by the researcher); real-world events, but little control, like Charlton's St Helena study.
Other research methods include observations (watching behaviour, structured or naturalistic), questionnaires and interviews (self-report of thoughts and feelings, giving quantitative or qualitative data), and case studies (in-depth study of one person or small group, rich but hard to generalise, like Sperry's split-brain patients).
Try this
Q1. What does a null hypothesis predict? [1 mark]
- Cue. That there is no difference between conditions (any difference is due to chance).
Q2. Which design uses the same participants in every condition? [1 mark]
- Cue. Repeated measures.
Q3. Explain one weakness of a laboratory experiment. [2 marks]
- Cue. It can be artificial (low ecological validity), so behaviour may differ from real life.
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel 20193 marksWrite a suitable alternative (experimental) hypothesis for a study testing whether caffeine improves reaction time. (Paper 2)Show worked answer →
A 3-mark item rewards an operationalised, directional or non-directional hypothesis that is testable.
A suitable alternative hypothesis is: "Participants who drink a caffeinated drink will have a faster mean reaction time (measured in milliseconds on a reaction-time test) than participants who drink a decaffeinated drink." This is operationalised because it states how caffeine and reaction time are measured, and it predicts a difference between two conditions. A null hypothesis would state there is no difference in mean reaction time between the two groups, and any difference is due to chance.
Markers reward a clear, testable prediction that names the two conditions and operationalises the variables (how caffeine and reaction time are defined and measured).
Edexcel 20214 marksExplain one strength and one weakness of using an independent groups design. (Paper 2)Show worked answer →
A 4-mark Explain item rewards a developed strength and weakness of independent groups.
Strength: in an independent groups design, different participants do each condition, so there are no order effects (participants cannot get better through practice or worse through fatigue across conditions, because each person does only one). Weakness: because different people are in each group, individual differences between participants (such as differing ability or personality) might affect the results rather than the independent variable, reducing how fairly the conditions can be compared. This can be reduced by randomly allocating participants to groups.
Markers reward the explained strength (no order effects) and the explained weakness (participant or individual differences between groups), ideally noting random allocation as a control.
Related dot points
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A focused answer to Edexcel GCSE Psychology Topic 11, covering sampling methods (random, opportunity, stratified, systematic) and variables (independent, dependent, extraneous) and how they are controlled.
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A focused answer to Edexcel GCSE Psychology Topic 11, covering data analysis: types of data, measures of central tendency, the range, percentages, ratios and fractions, and displaying data.
- Ethical issues in psychological research: consent, deception, protection from harm, confidentiality and the right to withdraw, the use of animals, and how researchers deal with these issues.
A focused answer to Edexcel GCSE Psychology Topic 11, covering ethical issues in research: consent, deception, protection from harm, confidentiality, the right to withdraw, the use of animals, and how they are dealt with.
- Core studies: Bartlett (1932) War of the Ghosts and Peterson and Peterson (1959) on short-term memory duration, including their aims, methods, results, conclusions and evaluation, and the reductionism-holism debate.
A focused answer to the Edexcel GCSE Psychology Topic 2 core studies: Bartlett (1932) War of the Ghosts and Peterson and Peterson (1959) on short-term memory, with aim, method, results, conclusion, evaluation and the reductionism-holism debate.
- Core studies: Sperry (1968) on split-brain patients and Damasio et al. (1994) on the case of Phineas Gage, including their aims, methods, results, conclusions and evaluation.
A focused answer to the Edexcel GCSE Psychology Topic 4 core studies: Sperry (1968) on split-brain patients and Damasio et al. (1994) on Phineas Gage, with aim, method, results, conclusion and evaluation.
Sources & how we know this
- Pearson Edexcel GCSE (9-1) Psychology (1PS0) specification — Pearson Edexcel (2017)