What is the proper process for grouping data by a category and computing an aggregate?

What is the proper process for grouping data by a category and computing an aggregate?

• A. Merge All Categories Into a Single Set and Compute One Statistic
• B. Compute the Statistic for the Entire Dataset, Ignoring Category
• C. Group By Category and Ignore the Statistic
• D. Split Into Groups by the Category and Calculate the Chosen Statistic for Each Group

Answer: (D)

Grouping data by a category and computing an aggregate means splitting the data into those category-based groups and applying the chosen statistic within each group. This approach keeps the category distinctions visible and gives a summary for every category, which is exactly what you need when you want to compare how the statistic differs across groups. If you merge all categories into one set, you lose the category information and get a single overall value. If you compute the statistic on the entire dataset without grouping, you ignore category differences entirely. If you group by category but don’t compute a statistic, there’s no summarized measure to compare across groups. The right method is to split into groups by the category and calculate the statistic for each group, yielding a clear per-category summary.

Grouping data by a category and computing an aggregate means splitting the data into those category-based groups and applying the chosen statistic within each group. This approach keeps the category distinctions visible and gives a summary for every category, which is exactly what you need when you want to compare how the statistic differs across groups. If you merge all categories into one set, you lose the category information and get a single overall value. If you compute the statistic on the entire dataset without grouping, you ignore category differences entirely. If you group by category but don’t compute a statistic, there’s no summarized measure to compare across groups. The right method is to split into groups by the category and calculate the statistic for each group, yielding a clear per-category summary.