If your data represents the only a sample of the entire population for the variable, then use the VAR_SAMP function. For information, see “VAR_SAMP”.

As the sample size increases, the values for VAR_SAMP and VAR_POP approach the same number, but you should always use the more conservative STDDEV_SAMP calculation unless you are absolutely certain that your data constitutes the entire population for the variable.