Reliability A measure of consistency. Can we get the same results when the same measure is used on another occasion? Measures in research should be reliable so that they can be replicated or repeated.

Internal reliability A measure of the extent to which something is consistent within itself. E.g. all of the questions on an IQ test should be measuring the same thing.

External reliability A measure of consistency over several different occasions. E.g. If an interviewer conducted an interview, and then conducted the same interview with the same interviewee a week later, the outcome should be the same.

Validity The extent to which something is true or real. 1.Internal: control and realism. 2.External: generalising.

Internal validity What goes on inside a study. 1.Whether the IV produced the change in the DV rather than other factors, such as extraneous variables. 2.Whether the study has tested what it set out to test. E.g. does IQ score measure intelligence? To gain high internal validity you must design the research carefully, controlling extraneous variables, and ensuring you are testing what you intended to test. May be threatened by demand characteristics

Internal validity 1.Face validity: Does the test look as if it is measuring what the researcher intended to measure? 2.Concurrent validity: This can be established by comparing the current test with a previously established test on the same topic. PTs take both tests and then the 2 test scores are compared.

External validity Whether the results are valid outside of the experimental setting. Can they be generalised to other situations, people and over time? 1.Ecological validity – can the findings be generalised to different places/settings? 2.Population validity – can the findings be generalised to different people or populations? 3.Time/historical validity – can the findings be generalised to different times?

Independent task Complete the next page in your booklet. 1.4 questions on reliability and validity. 2.Colour code activity.

Pair task Apply your knowledge of validity and reliability to the 4 research studies.