If each row in a dataset represents a single purchase, which approach would count the total number of purchases?

• A. Use a SUM function on the purchase amounts.
• B. Use COUNTA on the purchase ID column.
• C. Use AVERAGE on the purchase IDs.
• D. Use MAX on purchase IDs.

Answer: (B)

Counting how many purchases happened comes from counting the records, not summing values or averaging identifiers. Since each row represents a purchase and each row has a purchase ID, counting the non-empty IDs gives exactly one count per purchase. That’s what a function that counts non-empty cells in a column does: apply it to the purchase ID column and you get the total number of purchases. Using the sum on purchase amounts would give total revenue, not count; the average on IDs would mix values and not reflect quantity; and the maximum ID would just return the largest identifier, not how many purchases there were. So counting the non-empty purchase IDs directly yields the total purchases.