Researchers who need to explain treatment effects to laypeople can translate Cohen's effect size (standardized mean difference) to a common language effect size--a probability of a random observation from one population being larger than a random observation from the other population. This common language effect size can be extended to represent…

Construct irrelevance (CI) and construct underrepresentation (CU) are 2 major threats to validity, yet they are rarely discussed within the counseling literature. This article provides information about the relevance of these threats to internal validity. An illustrative case example will be provided to assist counselors in understanding these…

Precision is a key facet of test development, with score reliability determined primarily according to the types of error one wants to approximate and demonstrate. This article identifies and discusses several primary forms of reliability estimation: internal consistency (i.e., split-half, KR-20, a), test-retest, alternate forms, interscorer, and…