Any psychological test should have certain psychometric properties & meet generally accepted standards of what a satisfactory assessment instrument should be. However, the scores individuals receive on these instruments also depend on such factors as whether they are upset or unsure about what is expected in the situation. Formal features of assessment situations include the psychometric properties of the instruments applied. The informal features are the observations of the person being address, which may have more to do with characteristics the person brings to the situation.
1. Reliability - An assessment instrument should show consistency, that is, barring a change, the scores obtained on a retest should be similar to those on the original test. A reliable test is consistent even though different clinicians are involved & the assessment situations take place at different times & conditions.
2. Validity - Is the test doing what it wa designed to do? The validity of an assessment instrument refers to the degree to which it's fulfilling its function. Validity is established when there is strong relationship between a test & appropriate independent criteria.
3. Norms - Psychological tests often have no predetermined standards of passing or failing performance. Rather an individual's test score is interpreted by comparing it with the scores obtained by others on the same test. Norms are established by the availability of scores for a group of typical people. Norms do not necessarily refer to the most desirable or ideal performance.
4. Norm sampling - Norms are as good as the groups from which they are derived. A distinction is made between a sample & the population from which the sample was drawn. The sample on which the norms are based should be large enough to provide stable values & be representative of the population under consideration. A test designed for universal use, for example throughout India, should optimally have norms based on a normative group that includes the major segment of country's population.