The test-retest method assesses the external consistency of a test. The timing of the test is important if the duration is too brief, then participants may recall information from the first test, which could bias the results.Īlternatively, if the duration is too long, it is feasible that the participants could have changed in some important way which could also bias the results. This is an example of why reliability in psychological research is necessary, if it wasn’t for the reliability of such tests some individuals may not be successfully diagnosed with disorders such as depression and consequently will not be given appropriate therapy. 93 therefore demonstrating high test-restest reliability of the depression inventory.

(1996) studied the responses of 26 outpatients on two separate therapy sessions one week apart, they found a correlation of. The disadvantages of the test-retest method are that it takes a long time for results to be obtained.īeck et al. If the same or similar results are obtained, then external reliability is established. It measures the stability of a test over time.Ī typical assessment would involve giving participants the same test on two separate occasions. Examples of appropriate tests include questionnaires and psychometric tests. Therefore the split-half method was not be an appropriate method to assess reliability for this personality test. This means it would not be appropriate for tests that measure different constructs.įor example, the Minnesota Multiphasic Personality Inventory has sub scales measuring differently behaviors such as depression, schizophrenia, social introversion. However, it can only be effective with large questionnaires in which all questions measure the same construct. The split-half method is a quick and easy way to establish reliability. 25) should either be removed or rewritten. For example, any items on separate halves of a test with a low correlation (e.g., r =. The reliability of a test could be improved by using this method. If the two halves of the test provide similar results, this would suggest that the test has internal reliability. A test can be split in half in several ways, e.g., the first half and the second half or by odd and even numbers.

This is done by comparing the results of one half of a test with the results of the other half. There, it measures the extent to which all parts of the test contribute equally to what is being measured. The split-half method assesses the internal consistency of a test, such as psychometric tests and questionnaires.

Reliability of psychometric tests