Which statistic is NOT included by default in PROC MEANS?

The statistic that is not included by default in PROC MEANS is the median. By default, PROC MEANS calculates several key statistics for numeric variables, which include the mean, standard deviation, minimum, maximum, and count of non-missing values. The mean is the average of the data, standard deviation measures the amount of variation or dispersion, and the mode represents the value that occurs most frequently.

However, the median, which is the middle value of a data set when sorted in ascending or descending order, is not part of the default output from PROC MEANS. If a user wishes to include the median in their analysis, they must explicitly request it by using the OPTIONS statement or the appropriate keyword within the PROC MEANS procedure. This is important because it highlights a key understanding of PROC MEANS: while it provides a robust set of statistics by default, certain measures, like the median, require specific instruction to be included in the results.