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Reliability and Validity

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Presentation on theme: "Reliability and Validity"— Presentation transcript:

1 Reliability and Validity

2 What does it mean? In pairs, think of how we use the words reliability and validity in everyday life. What do these words mean? Is there a difference between them or do they mean the same thing?

3 Reliability When assessing the reliability of a study, we generally need to ask two questions Can the study be replicated? If so, will the results be consistent? High vs low reliability

4 Measuring Reliability
Match the method of estimating reliability to the description (pg165) Test-Retest reliability If the measure depends upon interpretation of behaviour, we can compare the results from two or more raters. If the results in the two halves are similar, we can assume the test is reliable Split Half Reliability Splitting a test into two halves, and comparing the scores in both halves If the results on the two tests are similar, we can assume the test is reliable Inter-Rater reliability The measure is administered to the same group of people twice If there is high agreement between the raters, the measure is reliable

5 Validity Control Realism Generalisability Realism vs Control
Did the IV cause the DV? Realism Does the experiment reflect real life? Mundane realism Generalisability Can we generalise our results to the general population? Realism vs Control

6 Types of Validity Internal validity External Validity
What happens inside the study. External Validity How our results can be generalised beyond the study Validity of psychological measures How well our methods of measurement actually measure what we intend

7 Internal Validity Mundane realism Extraneous variables Task A and B
Situational variables Participant variables Investigator effects Demand characteristics Participant effects Task A and B Name the variables What are the EVs and how could they have been controlled?

8 External Validity Read pg and fill in the gaps

9 Validity of psychological measures
Operationalisation of variables Can result in loss of validity

10 Validity of psychological measures
Content validity Does the method used actually seem to measure what you intended? Concurrent validity How well does the measure agree with existing measures? Construct validity Is the method actually measuring all parts of what we are aiming to test? Predictive validity Is our measure associated with future behaviour?

11 Validity of psychological measures
Complete tacks C, D and E.


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