What does a margin of error of four points cost?
Precision is the most expensive line on a research brief and usually the least discussed. This template prices it: 601 responses at ±4, 2,401 at ±2, and the invitations you must send to land either.
Marketing Starter Sample Size (General) free
After you install, this is the model to open.
How Many People Do We Have to Ask?
- In your spreadsheet, click the Sortia icon in the strip of icons down the right-hand edge. No strip? Click the arrow at the bottom-right to open it. You can also use Extensions, then Sortia, then Open Sortia.
- Click Start from a template and put that name in the search box.
- Pick the card with that name and click Load this template. It arrives on a new tab with real numbers already in it.
The answer
The answer does not depend on how many customers you have, which is the first thing that surprises people:
- Responses needed
- 601 at ± 4 points
- Fieldwork cost
- $5,409 at $9 a response
- At ± 2 points
- 2,401 responses, $21,609
- Invitations to send
- 4,293 at a 14% response rate
Twice the precision costs four times the fieldwork, so decide what the answer will be used for before you pick a margin: a board line that says "roughly two thirds" is a ±10 survey at 97 responses, and a decision that turns on whether the number cleared 60% is a ±2 survey at 2,401. The trap at the bottom of the sheet is the one that ruins timetables: the tool gives you completes, never sends, and at a 14% response rate 601 completes means 4,293 invitations. If the population really is small, say it: entering 2,400 takes the requirement down to 481.
The model
One survey, one promise, and a ladder of margins beside it. The Sample Size (General) tool answers the headline case in a click, and the sheet prices the neighbouring choices at your own cost per response.
| What is being estimated | the share who would recommend |
| Margin of error promised | ± 4 points |
| Confidence | 95% |
| Best guess at the answer | 50%, the worst case |
| Cost per response / response rate | $9 / 14% |
Once it is in your sheet
- The model arrives with real numbers in it and runs as it stands, so you can press the button first and understand it second.
- Change the numbers to yours. The sheet marks which cells are inputs and which hold formulas, and most labels carry a note explaining the row.
- Press the run button at the bottom of the panel. It is labeled for the tool you are in, and the result lands on its own tab, with a written reading of it beside the figures.
Never used Google Sheets? Start here goes the whole way, in seven steps, and assumes nothing.
Next question
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Every model like this one, and the method behind them: Statistics in Google Sheets.