Reliability and Validity of a Test - Assignment Example

Write a description of one method for estimating the reliability and one method for substantiating the validity of a test. Discuss the conditions under which each method is appropriate and or inappropriate. Explain the importance of reliability and validity. Reliability of a test refers to the possibility of arriving at the same conclusion by two or more people from a test conducted on a similar situation. Reliability testing can be test-oriented or rater-oriented. For example, test-retest is a common method of measuring reliability in which the test is applied more than one time in order to measure the reliability of features exhibited by a person.

For the diagnosis to be termed accurate, the features identified have to be same every time if the test is to be termed reliable. This is measured by a correlation between the two test outcomes over all the participants. This method expresses the generalisability of the test scores over different test occasions by assessing the stability of the test outcomes (Hempel, 2005). Hempel (2005) explains that this method of testing reliability varies with the type of tests, i.e. ability or traits and attitudes or states assessment.

In both cases, repetitive responses based on previous memory is a high possibility thereby giving incorrect measures of reliability. Secondly, the traits tend to change with time, and this would depict low-reliability measure, which is again incorrect (Garb, 2002). In such cases, the time period between the tests needs to be recorded appropriately in order to obtain an accurate reliability measure.