The Science of Human Behavior, Measured.
Articles on measurement theory, IRT, CFA, and test development
Say you’ve found a well-validated English questionnaire, a depression scale, a personality inventory, a measure of job satisfaction, and you want to use it in your own country, in your own language. The obvious first move is to translate it. Get a good translator, convert the items, and start collecting data. This is exactly the … Read more
If you’ve studied statistics in a psychology program, you learned classical test theory, even if nobody called it that. Reliability, Cronbach’s alpha, total scores, item-total correlations: all of it belongs to the classical framework. It’s the water most researchers swim in. But there’s another framework, one that underlies nearly all modern large-scale testing – the … Read more
The Likert scale is the workhorse of psychology and the social sciences. “I feel confident in my abilities: strongly disagree, disagree, neutral, agree, strongly agree.” Assign the numbers 1 through 5, collect responses, compute means, run correlations, publish. It’s so familiar that most researchers never stop to think about what they’re actually doing. They should. … Read more
Every test, every scale, every measurement instrument in psychology and education starts with the same humble unit: the item. A single question, a single statement, a single decision point. Get the items right, and your measurement has a chance. Get them wrong, and no amount of sophisticated statistics will save you. Yet item writing is … Read more
If you teach, you give tests. Quizzes, midterms, finals, classroom assessments. They’re a core part of how we measure what students have learned. But here’s a question most teachers never ask: how good are your tests, actually? Most assessment in education is built on intuition. A teacher writes questions that seem fair, grades the results, … Read more
Imagine I bring a bathroom scale into the room and tell you it measures height. You’d laugh. The instrument is wrong for the construct. It doesn’t matter how precise the scale is, how consistent its readings are, or how trustworthy the brand is, if I’m using it to measure height, I’m wrong. Now imagine I … Read more
If you’ve ever taken a personality quiz online – one of those “Which Harry Potter character are you?” tests, or a viral “What does your favorite color say about you?” quiz – you’ve engaged with something that looks like psychological assessment but isn’t. These quizzes are entertainment. They have no scientific basis, no validated psychometric … Read more