gcse psychology reliability vs validity

Reliability: consistency in measurement

You can test it by doing test-retest reliability or inter-rater reliability. Let me give you an example...

Test-retest---> If you are making a diagnosis for example you should make the same diagnosis regardless of when it was e.g. you should make the same diagnosis now as you did yesterday.

Inter-rater reliability ---> If you had two people diagnosing the same person they should both reach the same diagnosis- this suggests the diagnosis is reliable

Validity: how legitimate something is as an explanation of behaviour

There are two types:

Internal validity: whether the effects observed in the experiment were a consequence of the manipulation of the independent variable

External validity: whether you can generalise the results of the study
This also concerns:
1) Ecological validity- the place where the research was conducted. Can you generalise the research setting to everyday life? If the setting was a laboratory then it's won't be generalisable.
2) Population validity- the people who are studied. Can you generalise the findings to all people? If the sample is just of students then you can't.
3) Historical validity- the historical period. Can the findings of the study in the 1950s be applied today?