Question 1

What is the difference between a lab experiment and a field experiment?

Accepted Answer

A lab experiment takes place in a controlled environment where the researcher manipulates the IV and controls extraneous variables. This gives high internal validity but low ecological validity. A field experiment occurs in a natural setting (e.g., a school or street), so it has higher ecological validity but less control over confounding variables, making replication harder. Both involve random allocation to conditions, unlike natural experiments.

Question 2

How do I choose which statistical test to use in my A-Level psychology research?

Accepted Answer

You need to consider three things: the experimental design (independent groups, repeated measures, or matched pairs), the level of measurement (nominal, ordinal, or interval), and whether you're looking for a difference or a correlation. For example, if you have repeated measures and ordinal data looking for a difference, use the Wilcoxon signed-rank test. A common mnemonic is 'S for Spearman (correlation), W for Wilcoxon (related difference), M for Mann-Whitney (unrelated difference), and C for Chi-squared (nominal data).'

Question 3

What is the difference between reliability and validity?

Accepted Answer

Reliability refers to consistency—if you repeat the study, do you get the same results? Validity refers to accuracy—does the study measure what it claims to measure? For example, a broken thermometer that always reads 20°C is reliable (consistent) but not valid (inaccurate). In psychology, you can improve reliability by using standardised procedures and test-retest methods, and validity by using control groups and double-blind designs.

Question 4

What is a confounding variable and how do I control it?

Accepted Answer

A confounding variable is an extraneous variable that varies systematically with the IV, affecting the DV and making it impossible to determine causation. For example, if you test memory in the morning for one group and afternoon for another, time of day is a confound. Control methods include random allocation (to distribute participant variables), standardisation (same instructions, environment), and counterbalancing (for order effects in repeated measures).

Question 5

How do I write a hypothesis for my psychology practical?

Accepted Answer

A hypothesis must be operationalised—state exactly what you are measuring and how. For a directional (one-tailed) hypothesis, predict the direction of the effect (e.g., 'Participants who listen to classical music will recall significantly more words from a list than those who listen to white noise, as measured by the number of words correctly recalled in 2 minutes'). For non-directional (two-tailed), just state there will be a difference (e.g., 'There will be a significant difference in word recall between participants who listen to classical music and those who listen to white noise'). Always include the DV and the population.

Question 6

What is the difference between a type I and type II error?

Accepted Answer

A Type I error (false positive) occurs when you reject the null hypothesis when it is actually true—you think there is an effect when there isn't. This is more likely if you set a lenient significance level (e.g., p < 0.10). A Type II error (false negative) occurs when you accept the null hypothesis when it is false—you miss a real effect. This is more likely with a small sample size or a strict significance level (e.g., p < 0.01). Psychologists typically use p < 0.05 to balance these risks.

Research methods (Component 01)

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Related Topics in OCR A-Level Psychology

Applied psychology (Component 03)

Data recording, analysis and presentation

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How science works

How to Revise Research methods (Component 01) — OCR A-Level Psychology

Examiner Tips for Research methods (Component 01)

Common Mistakes in Research methods (Component 01)

Key Marking Points