What is the purpose of the CLASS statement in PROC MEANS?

The purpose of the CLASS statement in PROC MEANS is to specify grouping variables for statistical analysis. When you include one or more variables in the CLASS statement, SAS will calculate statistics separately for each level of the categorical variables you define. This allows for a more nuanced understanding of the data by providing summary statistics like the mean, standard deviation, and count for each subgroup identified by the levels of the specified CLASS variables.

Using the CLASS statement is particularly useful when you want to analyze how different categories in your data affect the statistical measures you are calculating, enabling insights that might be obscured in overall summaries. For instance, if you want to analyze how different regions or demographic groups are performing, using the CLASS statement will effectively segment the results accordingly.

In contrast, defining an output dataset relates to the OUTPUT statement rather than the CLASS statement, applying formats concerns presenting the results and does not affect how data is grouped, and creating a new variable would involve programming with a DATA step or using the CALL EXECUTE routine and is not within the parameters of PROC MEANS. Thus, the CLASS statement is specifically designed for the purpose of grouping data for statistical analysis.