Final answer:
The first step using the DATA step to summarize grouped data is to set the accumulating variable to zero at the start of each BY group. This step ensures accurate calculations for each group independently.
Step-by-step explanation:
When using the DATA step to summarize grouped data in SAS or a similar statistical software, the first step in the process is b. Set the accumulating variable to zero at the start of each BY group. This step ensures that you are starting a fresh calculation for each group of data. In the context of collecting averages of groups of five or organizing other grouped data, it is critical to reset accumulators at the start of each new group to avoid carrying over data from previous groups and potentially skewing the results.
Before you begin the summarization process, you'd also want to make sure all your observations are recorded accurately. This could involve recording data manually in a table or entering the data values into a list on a graphing calculator. The key to successful analysis is to start with correctly organized data to perform descriptive statistics correctly, and when required, apply inferential statistics.