Matthew Zack responded:

Kappa is usually calculated on the basis of categorical data. How do you group your information (for example, V events; duration/start or stop times) into categories? As the number of categories increases, the theoretical maximum kappa decreases.

Does the ID code identify nursing home residents or raters? Does the primary/rely code identify raters?

My response: Our kappa calculations are based on the number of seconds of agreement between the two raters for a specific key. So there would be a kappa for every key involved. The equation we use is a modification of the categorical one (I believe) where kappa is the proportion of number of agreement and nonagreement seconds divided by the total number of seconds of the file. I'm not entirely clear where we found this modification, but it is an acceptable form for the research we do. In the sample dataset, I only included the code for Primary/Rely. In the real dataset, we have the raters' initials.

John Gerstle Program Analyst, Sr. Applied Gerontology Program University of Alabama