Selection of random samples out of virtual cohorts

As a researcher I want to create random samples with a pre-defined sample size from a transferred virtual cohort.

> If an imported datafile has been selected, a list with options should occur: “full dataset” or “random sample”. If random sample is selected, it should be possible to enter the desired sample size. In a next step a random sample of the given size is selected from the datafile, stored, and used for further analysis.