OM book glossary

This is the glossary for the book “Outcome measures and evaluation in counselling and psychotherapy” written by myself and Jo-anne Carlyle and available now from SAGE. I am over 430 entries now and still climbing though now (April 2026) I am concentrating more on harmonising, cleaning up and cross-linking existing entries than I am on adding new ones. Some glossary entries link to more detailed expansions of the topic in my Rblog and, at last, an increasing number now link with interactive online (“shiny”) apps.

You can see the alphabetical list of entries below which is a good place to browse, or you can use this search box.

Beware: the way the search orders the matches is to my mind bizarre so scroll down if what you typed isn’t first on the list, you may find something with exactly the title that is exactly the phrase you typed in to find is hidden down the list of suggestions.

If what you want is not there and you think it should be, contact me and tell me and I will put it on the (long!) list of entries to be added!

A

Approximation

Yes, it's about having "good enough" precision. Numeric, or numerical, approximation: the way much…

Analysis of covariance (ANCOVA)

A very simple extension of the ANOVA model. Instead of analysing the values of…

Analysis of variance (ANOVA)

This is a huge family of statistical analyses within the NHST (Null Hypothesis Significance Test…

Autocorrelation

To some extent it's what it says: how much something correlates with itself but what…

Abstracteeism

A neologism created by Branca Sa Pires and leapt upon by me in one of…

Attenuation (by unreliability of measurement)

This is the very basic reality that if you have unreliable measures of things, and…

Accuracy

What it means in everyday language really. It's one of two parts of observational…

Average absolute deviation (AAD)

This is generally used to describe a family of measures of dispersion, i.e. of the…

Alpha

First letter of the Greek alphabet. OK, OK, I know you knew that! It…

Anderson-Darling test

A good test of distribution fit. (That's a graphic from my Rblog post about…

More

Creation date lost, updated 19.v.24 to add the new BetterDocs “encyclopedia” listing of entries, tweaks 13.iv.26. Author CE; this page and all glossary contents are copyright to me so contact me if you want to quote from them (I’m sure I’ll agree!). That may change to a Creative Commons licence later when I am happier with the content.