1. Reliability and Validity Themes in Psychology

2. Reliability Reliability of measurement instrument: the extent to which it gives consistent measurements Reliability of methodology: the extent to which it can be repeated and produce the same result. Consistency! How can we increase the reliability of; – 1) Experiment? – 2) Questionnaire? – 3) Observations?

3. Checking Reliability 1) Controlled Experiment: An experiment with careful control of extraneous variables and an appropriate sample should ideally have high reliability if replicated 2) Test-re-test method: A questionnaire can be done given to the same person on two different occasions to check if the results are similar. 3) Split half method: A questionnaire can be split in half (odd/even Qs) and both halves can be given to the same participant. The scores of both sections should be the same 4) Inter-rater reliability: Observations can be undertaken by two or more different independent observers. Statistics can then be applied to check the agreement (correlation) between them.

4. Validity Validity: the extent to which an experiment or procedure for collecting data actually measures or tests what it claims to test or measure. We can check validity by; 1) Construct Validity: Compare research data with theoretical ideas about what it is supposed to be measuring. 2) Criterion Validity: Compares the measure with some other actual measure taken at the same time (concurrent validity) or at a later date (predictive validity). 3) Face Validity: the degree to which a test or measure appears to superficially measure what it is supposed to