Re: the midpoint

Jacqui Costigan (
Thu, 6 May 1999 12:46:52 +1100

>Recently I was having an e-mail discussion regarding the midpoint, as often
>used in repertory grids. The midpoint can denote either a middle value or
>that the construct is not applicable (NA). These are different issues,
>though at times the midpoint is used as a catchall for both issues.
>As I understand it options include:
>a) forced choice/don't include a midpoint
>b) the midpoint is labelled, as a bit like both etc or a bit like neither
>or NA
>c) transform the scale into a unipolar scale, with 0 = NA etc
>d) treat NA as a missing value, though I'm not sure of grid programs that
>allow for this.
>I would be interested to hear other suggestions or preferences,
>Bob Green


I did a study in 88 comparing 5 with 6-point grid rating scales.

I asked what the midpoint meant for the 5-pt group. It was either, neither
or both ends, don't know, don't want to answer or stuff you. So I don't use
those overinclusive midpoints any more.

See Yorke,M. (1983). Straight or bent: an inquiry into rating scales in
repertory grids. BRITISH EDUCATIONAL RESEARCH JOURNAL. 9:2 141-151

If you like I could rake up my old paper.


Jacqui Costigan
Senior Lecturer in Applied Psychology
School of Public Health
La Trobe University, Bundoora 3083
Phone: 9479 5799. Fax: 9479 1783 Mobile: 0419 511 283