Criterion validity, construct validity, and factor analysis: An introductory overview.

This is the fourth and last article in the series on translation, adaptation, or development of a rating scale and its psychometric testing. The focus of this article is on criterion validity, construct validity, and factor analysis. Validity refers to whether the tool measures "what it purports to measure." Content validity, criterion validity, and construct validity are the different types of validity. Content validity was previously discussed in this series. Criterion validity assesses how a new scale correlates with a criterion or "gold standard." Depending on the time of administration of the "gold standard," this can be classified as concurrent or predictive validity. Pearson's correlation coefficient is the measure used to establish criterion validity for continuous variables, while phi coefficient is used for dichotomous ones. Construct validity assesses whether the new tool performs consistently with the theoretical concepts. This can be of two types: convergent and divergent validity, and is estimated using Pearson's correlation coefficient. Factor analysis (FA) is a multivariate technique that evaluates whether several variables are linearly related to a set of factors. It is also a method to assess construct validity. There are two methods of FA: exploratory and confirmatory FA; the steps of exploratory FA are discussed in detail here.