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CONFIDENCE Function
Summary
The CONFIDENCE function calculates the margin of error for a population mean using normal distribution assumptions. It helps determine the range within which the true population mean likely falls, based on sample data and a specified confidence level.
Syntax
CONFIDENCE(alpha, standard_dev, size)Parameters
| Parameter | Type | Required | Description |
|---|---|---|---|
| alpha | Number |
Yes | Significance level used to compute confidence (e.g., 0.05 for 95% confidence) |
| standard_dev | Number |
Yes | Population standard deviation (must be > 0) |
| size | Number |
Yes | Sample size (integer ≥ 1) |
Using the CONFIDENCE Function
Use CONFIDENCE when you know the population standard deviation and want to construct a confidence interval around your sample mean. The result represents the margin of error: sample_mean ± CONFIDENCE(...). Ideal for quality control, survey analysis, and scientific research.
Common CONFIDENCE Examples
Basic Confidence Interval
=CONFIDENCE(0.05, 2.5, 50)Returns 0.69295 - margin of error for 95% confidence with std dev 2.5 and n=50. Sample mean ± this value gives the interval.
Survey Analysis
=CONFIDENCE(A1, A2, A3)A1=0.05 (95% confidence), A2=population std dev, A3=sample size. Creates interval for survey results.
Frequently Asked Questions
Common Errors and Solutions
#NUM!
Cause: Alpha ≤0 or ≥1, standard_dev ≤0, or size <1
Solution: Verify alpha between 0-1, positive std dev, sample size ≥1
#VALUE!
Cause: Non-numeric input
Solution: Ensure all arguments are numbers
Notes
- This legacy function assumes normal distribution and known population std dev
- Replaced by CONFIDENCE.NORM (normal) and CONFIDENCE.T (t-distribution)
- Size parameter truncates decimals to integer
- Microsoft recommends newer functions for future compatibility
Compatibility
Available in: Excel for Microsoft 365, Excel 2021, Excel 2019, Excel 2016, Excel 2013, Excel 2010, Excel 2007
Not available in: Excel 2003 and earlier
Content last reviewed: December 8, 2025
Update frequency: As needed
Excel versions tested: Excel for Microsoft 365, Excel for Microsoft 365 for Mac, Excel for the web, Excel 2024, Excel 2024 for Mac, Excel 2021, Excel 2021 for Mac, Excel 2019, Excel 2016