In the PROC UNIVARIATE procedure, what does the 'CLASS' statement define?

The 'CLASS' statement in the PROC UNIVARIATE procedure is used to define the grouping of analysis parameters. This statement allows you to specify categorical variables that will be used to create separate analyses within the procedure. By grouping data according to these categorical variables, PROC UNIVARIATE can provide separate statistics, such as means, standard deviations, and frequencies, for each level of the variable specified in the CLASS statement.

For example, if you have a study with groups based on treatment types, using the CLASS statement will allow you to analyze the distribution of a dependent variable separately for each treatment group. This feature is particularly useful in clinical trials, where different treatment arms may yield different results, allowing researchers to understand the impact of each treatment effectively.

This functionality is crucial for drawing meaningful comparisons and understanding how different factors influence the expected results in any given dataset, especially in clinical contexts.