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 if you are searching, the way that the plugin 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 word or phrase you typed in to find is hidden further down the list of suggestions. As of 29.ix.26 the plugin authors are aware and working on this.

As to the content, if a topic 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!

C

Card sort methods

There are a range of card sort methodologies in various disciplines, but they share asking…

Categorical/nominal data/scaling

This is about Stevens' typology of scales and it's probably the only bit of his…

Causality & causal attribution

Perhaps it's understandable that work committed to helping with human misery and self-destructiveness should want…

Ceiling effect

In OM this refers to most people choosing the maximum possible score on an item…

Cell and cell size

Mostly "cell" in statistical work refers to a group of observations sharing two or more…

Censored data

Censored data exists when the value of an observation is not fully known but is…

Census

A true or complete census is a complete dataset about a field of interest. …

Centiles

Synonym of "percentiles" and another name of quantiles really. Chapters Chapter 5 See also Much more detail in the…

Central location

A statistic for data from a continuous variable that summarise what it says: central location….

Centring/Centering

A bit esoteric but you may meet it in reports, particularly those using multi-level modelling…

More

Creation date lost, last updated 19.ix.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.