Question 1

What is the difference between a directional and non-directional hypothesis?

Accepted Answer

A directional hypothesis (one-tailed) predicts the specific direction of the relationship or difference between variables, e.g., 'Participants who listen to music will recall more words than those in silence.' A non-directional hypothesis (two-tailed) predicts a difference or relationship but does not specify direction, e.g., 'There will be a difference in word recall between music and silence conditions.' You choose based on previous research: if prior evidence strongly suggests a direction, use directional; if not, use non-directional to avoid bias.

Question 2

How do I choose which statistical test to use in an exam?

Accepted Answer

Use a decision tree: First, determine if your study is a test of difference (e.g., experiment) or correlation. For differences, check the experimental design: independent groups (use Mann-Whitney U or unrelated t-test), repeated measures (use Wilcoxon or related t-test), or matched pairs (use Wilcoxon or related t-test). For correlations, use Spearman's rho or Pearson's r. Then consider level of measurement: nominal data (Chi-squared), ordinal (Mann-Whitney, Wilcoxon, Spearman), interval (t-tests, Pearson). Always state the test and justify briefly.

Question 3

What are extraneous variables and how do I control them?

Accepted Answer

Extraneous variables are any variables other than the IV that could affect the DV, potentially confounding results. Examples include participant variables (age, mood), situational variables (noise, time of day), and experimenter effects. Control methods: random allocation to groups (for participant variables), standardisation of procedures (same instructions, environment), counterbalancing (for order effects in repeated measures), and double-blind designs (to reduce experimenter bias). In exams, identify specific extraneous variables relevant to the study and suggest controls.

Question 4

Why is peer review important in scientific processes?

Accepted Answer

Peer review is a quality control mechanism where experts evaluate research before publication. It checks for methodological flaws, ethical issues, and correct interpretation of data. This helps ensure that only valid and reliable research is published, maintaining the integrity of psychological science. However, peer review is not perfect—it can be biased, time-consuming, and may not detect fraud. Understanding its role and limitations is important for evaluating the credibility of studies.

Question 5

What is the difference between reliability and validity?

Accepted Answer

Reliability refers to the consistency of a measure—if you repeat the study or test, you get similar results. Types include test-retest reliability (same test, different time) and inter-rater reliability (agreement between observers). Validity refers to whether the test measures what it claims to measure. Internal validity is about cause-and-effect conclusions; external validity is about generalisability. A study can be reliable but not valid (e.g., a consistently inaccurate scale). In exams, you must evaluate both.

Question 6

How do I write a good evaluation of a research method?

Accepted Answer

Start by identifying the method (e.g., lab experiment, questionnaire). Then list strengths and limitations, using specific terminology. For example, for a lab experiment: strength—high control of extraneous variables increases internal validity; limitation—low ecological validity due to artificial setting, so findings may not generalise to real life. Always link to the study's findings and suggest improvements. Use a balanced approach: mention both sides and conclude on overall effectiveness. Avoid vague statements like 'it was good'—be precise.

Scientific processes

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How to Revise Scientific processes — AQA A-Level Psychology

Examiner Tips for Scientific processes

Common Mistakes in Scientific processes

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