ABSTRACT
Validity is a concept that is used in relation to measures, which is a generic term for measurement devices. When talking about measurement, especially in quantitative research, it is important to understand validity. Researchers call a measure valid to the extent that it measures what it is designed to measure and accurately performs the function(s) it is purported to perform. It is important to note that validity is relative to the purpose of testing. If the purpose is to measure the achievement of students exposed to instruction in critical thinking, a test that measures only factual knowledge will be largely lacking in validity. Consider some reasons why perfect validity is elusive. First, almost all tests tap only a sample of the behavior underlying the constructs being measured. Another reason that perfect validity is elusive is that some traits researchers may want to study are elusive and inherently difficult to measure.
