What can be used in combination with the RETAIN and OUTPUT statements to write only a summary record?

The option that allows you to write only a summary record in combination with the RETAIN and OUTPUT statements is the use of First. and Last. variables.

When processing data in SAS, First. and Last. variables are created in a DATA step when you use the BY statement. These special variables allow you to identify the first and last observations within each group of data. By combining these variables with the RETAIN statement—which holds values across iterations of the DATA step—and the OUTPUT statement—which explicitly writes data to a dataset, you can generate summary statistics per group effectively.

For instance, if you have a dataset sorted by a variable and you want to compute a summary (like a total or average) over a specific grouping, you can use the First. and Last. variables to determine when you’re at the beginning or end of a group. This gives you a way to output only the summary record (such as totals) at the last occurrence of each group while retaining any necessary accumulating values.

The other options do not directly achieve the same summarization effect when combined with RETAIN and OUTPUT statements. The SUM statement is often used to compute totals but does not specifically influence the output of records like the First. and Last. indicators. The OBS=