Check a few rows by hand
Meet the bakery sheet and the AI's formula, and check three rows by hand: one at the start, one in the middle, and one at the end.
Free course. Your Maestro, an AI, .
Say you keep a bakery's sales in Excel, on two sheets:
- Ventas (sales), with each product's code in column A and the quantity sold in column B.
- Precios (prices), with each product's code, name, and price, sorted by code.
Open the file you downloaded and look at them. Pay attention to P-260.
You ask the AI for a formula to bring in the price of each sale, and it gives you this one:
=VLOOKUP(A2,Precios!$A$2:$C$9,3)=BUSCARV(A2,Precios!$A$2:$C$9,3)If your Excel separates the parts with semicolons, change each comma to ;.
It reads like this: look up the code in A2 on the Precios sheet and bring back what's in the third column, the price. You drag it down. Every row has a price, another column multiplies quantity by price, and the total is 1,843. Not a single error.
Is it right? After the last page, you already know that "not a single error" doesn't answer that question.
Three steps to check it
You may already do these steps without thinking. You see a number and something doesn't add up. Write them down anyway. They work the same for your formulas. What you do without thinking, you can't hand off to anyone, not even to AI.
Step 1: check a few rows by hand
Pick a row, look up its code in Precios, and compare. The café de olla, P-210, costs 38, and that's what the formula brought back.
Do it with three rows spread apart: one at the start, one in the middle, and one at the end. The first rows are the ones you already saw when you dragged the formula down. Problems tend to be somewhere else: a product added later, a range that doesn't reach the bottom, something that changed halfway down the sheet. Spreading out your sample gives you a better chance of running into one.
If you land on a row with a code that isn't in Precios, you've found the problem. If not, the rows you check come out right, and that's why there are two more steps. Checking a few rows doesn't prove they're all right. It tells you early if something is badly wrong, and it makes you look at the data instead of the formula.
Try it
In your file:
- Put the AI's formula in column C of Ventas and drag it down.
- Pick three rows: one at the start, one in the middle, and one at the end.
- For each one, look up its code in Precios, read the price, and compare it with what the formula brought back.
- Write down which rows you checked and what you found.
A good answer says which three rows you picked, why those, and whether they all matched. If one didn't match, you're ahead: keep what you saw for page 5.
Tell your Maestro which rows you checked.