Learn how psychological measurement works.
Explore reliability, validity, norms, measurement, assessment design and interpretation. The objective is to make assessment science understandable without sacrificing methodological rigour.
Measurement is the least glamorous part of psychology and the part everything else rests on. Written well it is not difficult — reliability is a question about consistency, validity a question about whether you are measuring what you think you are, norms a question about who you are being compared with. This is where we explain those properly, for people who have to use instruments rather than build them.
4 articles
Newest first
What a percentile actually tells you
It is one of the most reported numbers in assessment and one of the most misread.
Reliability and validity, without the jargon
A test can be highly reliable and completely useless. The two words are not synonyms and the difference decides whether a report means anything.
Every score has a margin around it
A number reported to the decimal place invites a precision that no psychological measurement possesses.
Who is allowed to interpret a psychological test, and why the rule exists
Restricted access to instruments looks like gatekeeping. It is closer to a safety rule, and the reasons are worth stating.
