Douglas Mercer

Douglas serves as assessment and psychometrics editor. He covers psychometrics, test construction, item analysis, reliability and validity, and cognitive assessment. His work examines how test questions are designed, how scores are interpreted, and which claims the available evidence can support. He pays particular attention to the difference between a useful score and a score that appears more precise than the underlying measurement permits.

Before joining the desk, he worked in educational testing and item development. Much of that work involved reviewing items, studying response patterns, and checking whether assessments measured their stated constructs. It taught him to look beyond tidy score reports. An item can be clear yet measure the wrong skill. A test can be consistent without supporting the interpretation attached to it. He learned to examine the purpose, sample, administration conditions, and evidence before accepting a claim.

Douglas explains measurement by starting with its limits. He defines technical terms in plain language and separates what a score shows from what someone may infer from it. He treats reliability as a question about consistency under stated conditions, and validity as a judgment supported by several kinds of evidence. In every guide, he insists that the intended use of a test be stated before its quality is discussed. This keeps explanations tied to actual decisions rather than abstract numbers.