I have 4 experimental groups/conditions and 5 measurement times for each group/condition. Each participant only took part in one of the 1 conditions. In total there are 27 participants and each condition has around 6 participants.
In my data set, several participants are missing a value during one of the 5 measurement times. So there are several cases (rows) where the participant does not have 5 measurement times but only 4 for example. The missing values are completely random and exist in all conditions.
My problem is the following. Because SPSS does case-wise deletion I end up with around 6 fewer cases which severely impacts my results. What I am wondering is if it is feasible to impute the missing data using a regression for example. And how many values can I impute before it is no longer feasible?