Inter-rater reliability of time measurements I am having some trouble trying to decide what measure of inter-rater reliability to use in a study.  Part of a larger study involves accurately determining when participants began (onset) and stopped (offset) writing.  I have video footage which captures the writing, and can determine the time of onset/offset to the nearest 0.01 second.  The time is taken from a stopwatch which was running continuously from the start of each experiment, with multiple onset/offsets in each experiment. The onset/offset have been defined, and I would like to determine the inter-rater reliability for 2 raters.  The data looks like this:
Participant A  trial one - onset: 21.35 offset: 24.55
               trial two - onset: 54.50 offset 57.75
Participant B  trial one - onset 10.35 offset 21.15
               trial two - onset 35.65 offset 39.90

and so on and so forth.  Two raters would have data like the above and I would like to calculate if they are reliably similar.  I looked at Kappa statistic, Krippendorff’s alpha, intra-class correlation, etc., but none seems appropriate for continuous time measurements.
 A: It seems to me that what you're interested in is simply a measure of how much Rater 1's time measurements differ from Rater 2's, in which case you probably want to look at something simple like the root mean square difference in timings between the two raters. This will have the advantage of having an intuitive scale, being a measure (in seconds) of the typical difference between the two raters' timings.
A: Perhaps you could use a hierarchical linear model with elapsed time nested within individual and individual cross nested within rater (assuming at least some individuals are evaluated by more than one rater).  This would give you the variance at each level - with the variance at the rater level being the indicator of reliability/consistency.
I'm not positive on the exact structure of the data so forgive me if I'm missing something here.  
Are individuals evaluated by more than one rater?
Are you interested in the elapsed time or specifically the onset and the offset (as if they are independent of each other)?
