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CONFIDENCE
CONFIDENCE calculates the half-width of a confidence interval around a sample mean, assuming a normally distributed population with known standard deviation. Add and subtract the result from your sample mean to construct the full confidence interval, commonly used in survey analysis and scientific reporting.
Excel
=CONFIDENCE(0.05,15,30)Google Sheets
=CONFIDENCE(0.05,15,30)✓
Verified example
Computed by a real spreadsheet engine on the sample data below.
| Alpha | StdDev | N |
| 0.05 | 15 | 30 |
| 0.10 | 12 | 50 |
| 0.01 | 20 | 100 |
=CONFIDENCE(0.05,15,30)→5.3675824312
Try it with your data
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How it works
- 1Determine your significance level (alpha) — for a 95% confidence interval use 0.05.
- 2Know your population standard deviation and sample size.
- 3Enter =CONFIDENCE(alpha, standard_dev, size); add and subtract the result from the sample mean to get the interval bounds.
Need a version for your data?
Try: “Calculate the 95% confidence interval margin of error for our survey with 30 respondents”