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

The purpose of the CLASS statement in PROC MEANS is to calculate statistics for groups of observations. When you include a CLASS statement, the procedure will generate summary statistics such as mean, median, standard deviation, etc., for each distinct level of the specified categorical variables. This allows analysts to understand how different groups within the dataset behave and how they compare to one another.

By categorizing the data based on specified variables, PROC MEANS can segregate the analysis, enabling a more granular insight into the data as a whole. This functionality is crucial for exploratory data analysis, hypothesis testing, and generating reports where group comparisons are needed.

In contrast, other options mentioned do not accurately represent the role of the CLASS statement. While one may think that specifying variables to analyze may include some aspects of the CLASS statement's functionality, it primarily focuses on defining how the data should be grouped for the sake of statistical computation rather than just representing the variables themselves. Additionally, defining new variables and controlling output format are capabilities linked to other statements and options within PROC MEANS but are not the primary functions of the CLASS statement.