VALIDITY What is validity What are the types

VALIDITY What is validity? What are the types of validity? How do you assess validity? How do you improve validity?

What is validity? Definition: Validity refers to whether or not the investigation measures what it is supposed to measure.

What are the types of validity? Types of validity – internal and external Internal – again whether or not the study is really testing what it is supposed to test. External – to what extent can the findings of the study be generalised across people, places and time periods.

How do you assess validity? Internal: Consider the extent to which we have control over variables. Also, specifically for self-reports, observations or other tests there are the following ways of checking validity: • Face validity • Concurrent validity • Predictive validity External: • Consider the 3 types of validity by looking at where the study took place, when it was conducted and who the sample were. • Also, you can look at replications of the study - has the study been replicated with the same results in a different environment, at a different time and on a different sample?

How do you improve validity? Here are some ways to improve internal validity: • Control for variables (e. g. demand characteristics, investigator effects, participant variables) • Standardisation • Randomisation To improve external validity: Replicate the study in the same way but in a different environment, at a different time and on a different sample

Past exam question and example answer What is meant by ‘validity’? How could the psychologist have assessed the validity of the questionnaire used to measure the severity of symptoms? [4 marks] Eg: ‘Validity refers to whether or not the questionnaire measures what it is supposed to measure (1 mark). Concurrent validity would involve getting a Doctor to assess the symptoms (1 mark) and seeing how closely they match the score on the questionnaire (1 mark). If the two matched, the questionnaire would have high validity (1 mark).

RELIABILITY What is reliability? What are the types of reliability? How do you assess each type reliability? How do you improve reliability?

What is reliability? If a study can be replicated in the same way and it gains consistent results it can be said to be reliable.

Types of reliability • Researcher: Refers to the consistency of the researchers who are gathering the data E. G. In observations or self reports this is called inter-rater reliability • Internal: Refers to the consistency of the measures used within the study. • External: Refers to the extent to which a measure is consistent from one occasion to another.

Researcher reliability • Assessing: Compare observations of two observers and conduct a correlation to see if results are similar. • Improving: Training, operationalisation, conduct a pilot study.

Internal reliability • Assessing: Split-half method • The observation categories or questions on a questionnaire should be split in half randomly, and the two sets of responses for each half compared – they should indicate the same result. This can be more formally assessed by carrying out a correlation • Improving: • Look at particular questions that seem to be giving a different result and change them until the split half method indicates an improved correlation.

External reliability • Assessing: Test-retest • Giving the same participant the same questionnaire at two different times and giving them no feedback after their first answers; the time gap will need to be sufficient for them not to remember how they answered first time but not so long that they have changed in a way relevant to the questionnaire. The two sets of answers should be correlated • Improving: • Check individual questions from the test-retest that do not positively correlate, then change alter them and do another test-retest until they positively correlate.