Introduction
The concept of validity was first originated by Stanley and Campbell in 1966 and later elaborated further by Campbell and Cook in 1979. The concept of validity has a significant impact on how researchers evaluate their work. Validity refers to the extent to which to which a given test measures that which it claims to measure. It is important to evaluate the validity of a test to ensure accurate interpretation and application of test results. There are four main types of validity; construct validity, statistical validity, external validity and internal validity. This paper seeks to compare and contrast the characteristics of external, ...