What a spreadsheet is for

A spreadsheet is an argument with the working shown. That is the whole idea and it is why the skill transfers everywhere — to a budget, a fee comparison, a small business, a research project, a first job in almost any function. The numbers are the claim; the formulas are the reasoning; anyone can check both.

Which means the test of a good sheet is not whether it produces the right total. It is whether a second person can open it, see where every number came from, and disagree with a specific cell. A sheet nobody else can follow is not analysis, it is an assertion with decoration.