What does the SUM statement do in a DATA step?

The SUM statement in a DATA step is designed to calculate the sum of specified variables for each observation processed. When you use the SUM statement, it adds up the values of the specified variables across all observations in the dataset, effectively allowing you to create a new variable that reflects this cumulative total. This feature makes it an integral tool for generating summary statistics directly within the DATA step, ensuring efficiency in data manipulation and analysis.

For instance, if you are summing sales figures across different regions, the SUM statement would aggregate these values, enabling you to analyze the total sales for each observation effectively. The summation is performed on a row-by-row basis during data step execution, and it can handle missing values appropriately, treating them as zeros when computing the total.

Other options focus on different functionalities: assigning ranks relates to the RANK function or procedures like PROC RANK, creating new variables typically involves assignment statements or calculations with existing variables, and deleting observations is achieved using conditional statements or the DROP statement. Each of these functionalities serves a different purpose within the SAS programming context, showcasing the versatility of the language in managing and analyzing datasets.