Q: How do I evaluate a study's validity in an exam?

To evaluate validity, consider internal validity (did the IV cause the DV? Were there confounding variables?), external validity (can the findings be generalised to other settings, people, or times?), and construct validity (do the measures truly represent the concept?). For example, a lab study may have high internal validity but low ecological validity. Use specific examples from the study to support your points, and suggest improvements like using a more natural setting or a different sample.

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 independent variable (IV) and controls extraneous variables. This increases internal validity but may lack ecological validity. A field experiment occurs in a natural setting, where the IV is still manipulated but participants are often unaware they are in a study, increasing mundane realism. However, there is less control over confounding variables, which can reduce internal validity.

Question 2

How do I know which statistical test to use in my research?

Accepted Answer

Choosing a statistical test depends on your experimental design (independent groups, repeated measures, or matched pairs), the level of measurement (nominal, ordinal, interval), and whether you are looking for a difference or a correlation. For example, if you have independent groups and ordinal data, use the Mann-Whitney U test. If you have repeated measures and nominal data, use the Sign test. Always check the test's assumptions before applying.

Question 3

What is the difference between reliability and validity?

Accepted Answer

Reliability refers to the consistency of a measure: if you repeat the study under the same conditions, you should get similar results. Validity refers to whether the study measures what it claims to measure. A study can be reliable but not valid (e.g., a faulty scale that consistently gives the same wrong weight). To improve reliability, use standardised procedures; to improve validity, ensure your operational definitions are accurate and control for confounding variables.

Question 4

Why is informed consent important in psychological research?

Accepted Answer

Informed consent ensures that participants understand the nature of the study, what they will be asked to do, and any potential risks before agreeing to take part. It respects their autonomy and right to choose. Without it, participants may feel deceived or coerced, which violates ethical guidelines. In some cases, deception may be necessary, but then participants must be fully debriefed afterwards and given the right to withdraw their data.

Question 5

What is a null hypothesis and how do I know when to reject it?

Accepted Answer

The null hypothesis (H0) states that there is no effect or no relationship between variables. You reject it if your calculated test statistic exceeds the critical value from the statistical table at your chosen significance level (usually p < 0.05). This means the observed result is unlikely to have occurred by chance, so you accept the alternative hypothesis (H1). If the calculated value is less than the critical value, you retain the null hypothesis.

Question 6

How do I evaluate a study's validity in an exam?

Accepted Answer

To evaluate validity, consider internal validity (did the IV cause the DV? Were there confounding variables?), external validity (can the findings be generalised to other settings, people, or times?), and construct validity (do the measures truly represent the concept?). For example, a lab study may have high internal validity but low ecological validity. Use specific examples from the study to support your points, and suggest improvements like using a more natural setting or a different sample.

Topic 9: Psychological skills

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Topic 1: Social psychology

Topic 2: Cognitive psychology

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