What does the OUTPUT statement do in a DATA step?

The OUTPUT statement in a DATA step specifically serves the purpose of writing the current observation to a dataset. This means that whenever the OUTPUT statement is encountered in the DATA step, the values of the variables present in that observation are saved to the designated output dataset. This is crucial for managing which records you want to include from the data processing.

In a typical DATA step, without an OUTPUT statement, SAS automatically writes the current observation to the dataset at the end of the step. However, including the OUTPUT statement gives you more control; for example, you can use it to write specific observations conditionally or to create multiple datasets from a single DATA step by specifying different OUTPUT statements for each dataset.

The other choices relate to different functionalities within the SAS programming context. For example, defining the structure of the dataset is typically associated with the DATA statement or attributes specified in the dataset options. Retaining the value of variables is accomplished with the RETAIN statement, which keeps variable values from one iteration of the DATA step to the next. Lastly, generating a summary report is the function of procedures like PROC PRINT or PROC SUMMARY, rather than anything related to the OUTPUT statement.