When I select a sample using > Restrict, based in criterion and then > Use dummy variable all works fine, and I get the appropriate sub-set. When I then select > Random sub-sample from this subset, everything is fine as long as the number selected is less than the number of items that were selected on the first call.

However, there is a misleading message Number of observations to select (max x), where x is greater than the number of observations that were selected on the first call. Furthermore, if I specify a number larger than the number of obs that were selected, it executes the specified x. However, on occasions I do get the message Invalid number of cases. If I re-enter the same x then it goes through. It appears there's a problem in trapping this. Thanks.