What is the result of using the KEEP statement in a DATA step?

Using the KEEP statement in a DATA step retains only the specified variables in the dataset. When the KEEP statement is included, it directs SAS to only keep the listed variables while dropping all other variables from the dataset. This is particularly useful for managing datasets by minimizing the amount of data being processed or outputted, which can lead to improved performance and clearer datasets.

For example, if a dataset contains many variables but you are only interested in analyzing or exporting a few of them, you would use the KEEP statement to define just those variables you want to retain. This action simplifies the dataset and focuses your analysis on only the relevant information.

The other options do not reflect the function of the KEEP statement. It does not delete all variables, format variables for output, or merge datasets. Instead, it provides a means to selectively retain certain variables, making your dataset easier to work with when only specific data is needed.