... and variables measured just on one occasion. Hello, Amelia authors and users, I'm doing a longitudinal study on the motivational development after transition to secondary school. Some constructs, e.g. learning goal orientation, were measured at each of our three waves. Other characteristics were just measured on one occasion, some because they ought to be time-invariant (e.g. socioeconomic status), others because new questions and hypotheses developed after the first results (e.g. about the influence of parental support). For using the time series-option, I rearranged my data in SPSS so that I got one cell per variable and time point, and added a time index-variable. The values of the time-invariant variables were kept constant over the measurement occasions, e.g. each case got one and the same value for each time point. Also, I did the same for the other variables that were just measured on one occasion. Here is my problem: The imputations of missings in the time-invariant variables (respectively the one-time measurements) result in different estimations per time point. How should I deal with this information? Should I just take the first value or calculate the mean of the values? Or do I have to deal differently with the problem right from the beginning? Is it adequate to do with time-invariant variables the same as with time-variant variables just measured on one occasion? I would be grateful for some help, greetings from Germany, Felix Brümmer - Amelia mailing list served by Harvard-MIT Data Center [Un]Subscribe/View Archive: http://lists.gking.harvard.edu/?info=amelia More info about Amelia: http://gking.harvard.edu/amelia