How validity and reliability can be achieved in selection process?

When testing an applicant the scores of the tests, when given on different days, should remain consistent or close to the same on any given date. This means the selection is reliable. Validity is achieved by giving the applicant tests that simulate the work they will be expected to do. The decision to hire the person or not can be based on the individuals IQ related to some required trait (construct), or it can be criterion-related measurements of their tests: compared to other applicants (predictive), compared to current employees (concurrent) (Decenzo & Robbins, 2006, p. 188-189).

DeCenzo, D., & Robbins, S. (2006). Fundamentals of Human Resource Management, p. 188-189. New York: Wiley & Sons Inc.