# Select cases: Random sample

This dialog box allows you to select a random sample based on an approximate percentage or an exact number of cases. Sampling is performed without replacement; so, the same case cannot be selected more than once.

**Approximately.** Generates a random sample of approximately
the specified percentage of cases. Since this routine makes an independent
pseudo-random decision for each case, the percentage of cases selected
can only approximate the specified percentage. The more cases there
are in the data file, the closer the percentage of cases selected
is to the specified percentage.

**Exactly.** A user-specified number of cases. You must also
specify the number of cases from which to generate the sample. This
second number should be less than or equal to the total number of
cases in the data file. If the number exceeds the total number of
cases in the data file, the sample will contain proportionally fewer
cases than the requested number.

Selecting a Random Sample

- From the menus choose:
- Select Random sample of cases.
- Click Sample.
- Select the sampling method and enter the percentage or number of cases.