You can add columns of descriptive summary statistics for any numeric column in the source table by clicking the Statistics button and making a selection from the menu.

The Statistics menu gives these summary statistics for numeric columns:

The arithmetic mean of a column’s values. It is the sum of nonmissing values (and if defined, multiplied by the weight variable) divided by the Sum Wgt.

The sum of all weight values in a column. (See Column Properties in The Column Info Window.) Or, if no column is assigned the weight role, Sum Wgt is the total number of nonmissing values.

The standard error of the mean. It is the standard deviation divided by the square root of N. If a column is assigned the role of weight, then the denominator is the square root of the sum of the weights.