One of the workloads of a psychologist is to appropriately administer, score and interpret psychometric and projective tests. When giving psychological test to clients, there is a need to identify if the test is standardized, reliable, valid, sensitive, objective and feasible to administer. This paper intends to answer the question “What is more important in assessment, reliability or validity?” According to Myers and Hansen (2007) reliability means the consistency and dependability of measurement and experimental procedures while on the other hand, according to Cohen and Swerdik (2008) validity means the judgment regarding how well a test or measurement tool measures what it purports to measure. Both reliability and validity are necessary criteria for evaluating the quality of psychological assessment procedure and these two factors are partially related and partially independent (Gravatter & Forzano, 2009).
As psychometrician and future psychologist, I believe that both validity and reliability should be given importance in assessment because reliability is a prerequisite for validity. On the other hand, it is not necessary for a measurement to be valid, for it to be reliable. For example, a test for aggression cannot be valid unless it is reliable; however, measurement of my height can be reliable or consistent without being valid by claiming that it is a measure of my emotional intelligence. Since reliability is necessary (but not sufficient) for validity, and if the results of a psychological test are inconsistent or unreliable, then the validity of the test is also affected.
Cohen, R. & Swerdik, M. (2008). Psychological Testing and Assessment. (6th ed.). NY: McGraw-Hill.
Gravetter, F. & Forzano, L. (2009). Research Methods for the Behavioral Sciences. (3rd ed.). CA: Wadsworth.
Myers, A. & Hansen C. (2007). Experimental Psychology. (6th ed.). CA: Thomson/Wadsworth.