There are several assumptions in psychological testing. For example, behaviorist assumption that psychology is a science and hence ought to be tested using scientific methods is one of the major assumptions. In addition, there is an assumption that people are born blank and learn all the traits they portray. The mind acquires and outputs information jus as machines and that the brain is in sections that can be identified separately. Another assumption is that behavior is acquired during childhood and can be influenced by hormones the person secretes.
In psychological testing, the test seeks to establish a verdict on a given individual or phenomenon. It is, therefore, imperative that the tests ought to produce valid and reliable results. Validity is the degree or the extent that a concept, measurement, or a conclusion under investigation is accurate and represent the real world occurrence. In particular, the validity of a test measures the degree that a particular measurement measures what it was intended to measure. Reliability on the other hand is the consistency in the measurements. It is the measure of how a given process, tests or an experiment produces the same results. In this case, a high reliability results produces similar results under the same conditions of the experiment or testing.
Validity in psychological testing includes content validity-comprehensiveness of the elements under study and how they produce acceptable results. Criterion-based validity; the capability of predicting results based on the current results. Construct validity; the capability to measure the predetermined measurements (Reliability and Validity, n.d). Face validity is the measure of how realistic an experiment is. On the other hand, reliability is divided in to: internal and test-retest reliability. The internal reliability is the measure of the interrelationship among elements under investigation. Test-retest reliability is the measure of concurrence of the same investigation in different unit or environment. It is worth noting that both validity and reliability operate concurrently.
Reference
Reliability and Validity. Retrieved on October 24, 2014 from http://writing.colostate.edu/guides/page.cfm?pageid=1388
