What does an IF THEN statement do in SAS?

An IF THEN statement in SAS is designed to control the flow of execution in a data step based on specific conditions. When you use an IF THEN statement, SAS evaluates the condition provided. If this condition is true or met, the statement(s) following the THEN keyword will be executed. This functionality allows you to conditionally process data, making it an essential tool for creating customized data manipulations or filtering.

For example, if you have a dataset and you only want to perform a calculation for records where a certain criterion is fulfilled, the IF THEN statement ensures that the subsequent actions are only carried out for those qualifying records. This selective processing enhances efficiency and accuracy in data handling within SAS.

Other choices do not accurately describe the purpose of the IF THEN statement; it does not execute multiple statements simultaneously as that would require additional constructs like DO groups; it does not check for syntax errors, which is handled by the SAS compiler; and it certainly does not always run regardless of conditions, as it specifically depends on whether the condition is satisfied.