Getting the formula right.
HOW TO ASK
Describe your data layout and what you want.
"Column A has dates, column B has amounts, column C has categories. I want the total for each category in a given month."
WHAT TO SPECIFY
Which spreadsheet program Your column layout What to do with blanks and errors
THAT LAST ONE
Generated formulas frequently ignore empty cells and error values, producing wrong results silently.
"Handle blank cells and errors."
TESTING IT
On a small sample where you know the answer.
Apply it to everything only once verified.
FOR COMPLEX FORMULAS
Ask for an explanation alongside it.
"Explain what each part does."
That way you can maintain it later.
FOR ERRORS
Paste the formula and the error.
"Why is this returning an error?"
WHAT TO ALWAYS CHECK
Totals, against a manual calculation on a sample.
