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In this article
CONFIDENCE.NORM gives the ± margin around a sample mean for a chosen confidence level.
Syntax
=CONFIDENCE.NORM(alpha, standard_dev, size)| Argument | What it means |
|---|---|
alpha |
0.05 for 95% confidence. |
Examples
Example 1
=CONFIDENCE.NORM(0.05, 12, 100)About 2.35: the true mean is likely within ±2.35 of your sample mean.
CONFIDENCE.NORM in practice
Where you will use it
- Margin of error for a survey average
- Range for average delivery time
- Quick ± in reports
Worked example
95% margin of error: average ± this value.
| Std dev | Sample size | Formula | Result |
|---|---|---|---|
| 12 | 100 | =ROUND(CONFIDENCE.NORM(0.05,A2,B2),2) | 2.35 |
| 12 | 400 | =ROUND(CONFIDENCE.NORM(0.05,A3,B3),2) | 1.18 |
| 5 | 30 | =ROUND(CONFIDENCE.NORM(0.05,A4,B4),2) | 1.79 |
Results calculated in Excel.
Mistakes people make
| Mistake | What to do instead |
|---|---|
| Using it for small samples | Below ~30 use CONFIDENCE.T |
| Alpha vs confidence | 0.05 means 95% confidence |
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