# Linear and Quadratic Weighted Kappa SPSS Error

I am using both Linear and Quadratic weighted kappa to examine the extent to which two measures (a quantitative clinical interview, and a corresponding self-report questionnaire) agree at the item level. By this I mean that I am checking extent to which the score for each item on the clinical interview, matches the score to the corresponding item on the questionnaire. All items on both measures are rated on a frequency likert scale (ranging from 1 "never", to 6 "every day").

However, the SPSS package I am using keeps returning with the following error :

"All ratings are the same for at least one rater. This command is not executed."

I believe this is because in the case of one instrument, the interview has rated all participants as 1/"never".

How do I resolve this issue?

• The short answer is that you cannot calculate agreement here. Just report what happened in your report. It is quite common. – mdewey Aug 10 '17 at 15:03
• Thank you mdewey, do you have a reference or any resources where I read further about this limitation? – Alice Phillips Aug 17 '17 at 10:37

The problem is that where one or both of the raters gives the same rating to everybody you cannot compute $\kappa$. The usual recourse is to report percent agreement and ay why $\kappa$ was not available.