What does the MERGE statement do in a data step?

The MERGE statement in a data step is designed specifically to combine two or more data sets based on a common variable, also known as a key. When using the MERGE statement, SAS aligns the observations from the different datasets according to the values of the key variable(s). This allows you to create a new dataset that includes data from both original datasets, effectively enriching the resulting data with additional attributes.

To utilize the MERGE statement correctly, the datasets must be sorted by the key variable prior to merging; otherwise, the merge can result in unexpected combinations of records. This capability to merge datasets makes it an essential tool in data processing within SAS, enabling comprehensive integration of information for analysis.

In contrast, finding the mean of a variable pertains to statistical functions that aggregate data, filtering observations is achieved through specific condition statements, and sorting a dataset is a separate process that organizes data in a particular order. Each of these other functionalities serves different purposes in data manipulation and analysis.