What must you ensure before inserting subtotals in a data set?

Before inserting subtotals in a data set, it is crucial that the data is properly sorted in the desired column. When subtotals are applied, Excel calculates the subtotals based on the sorted groups in the specified column. If the data is not sorted, the subtotals may not accurately reflect the intended grouping, leading to incorrect summaries.

Proper sorting organizes the data so that all related entries are grouped together, enabling accurate calculations of numbers within those groups. This allows for effective analysis and reporting based on the hierarchy of the data.

While formatting the data as a table and ensuring no blank rows are present are beneficial practices, they are not specific prerequisites for inserting subtotals. Including all columns is also not necessary; subtotals can be calculated based on selected columns that contain the relevant data. Thus, the focus on sorting ensures that the subtotal function works correctly.