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CONFIDENCE.T Function
Summary
The CONFIDENCE.T function calculates the confidence interval for a population mean when the population standard deviation is known, using the Student's t-distribution. This is essential for statistical analysis when working with small sample sizes where the normal distribution assumption doesn't hold.
Syntax
CONFIDENCE.T(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 ≥ 2) |
Using the CONFIDENCE.T Function
CONFIDENCE.T is used in statistical analysis to determine the margin of error around a sample mean estimate. Multiply this value by the standard error to get the full confidence interval range. Ideal for business analytics, quality control, and research studies with limited sample data.
Common CONFIDENCE.T Examples
Basic 95% Confidence Interval
=CONFIDENCE.T(0.05,1,50)Returns 0.2842 - confidence interval for sample size 50, std dev 1, 95% confidence using t-distribution
Quality Control Example
=CONFIDENCE.T(0.1,2.5,30)90% confidence interval (alpha=0.1) for manufacturing process with std dev 2.5, n=30 samples
Survey Analysis
=CONFIDENCE.T(0.05,STDEV.S(B2:B101),100)95% confidence interval using sample std dev for 100 survey responses
Frequently Asked Questions
Common Errors and Solutions
#VALUE!
Cause: Non-numeric input in any argument
Solution: Ensure all arguments contain valid numbers
#NUM!
Cause: Alpha ≤ 0 or ≥ 1, or standard_dev ≤ 0
Solution: Use alpha between 0 and 1 (exclusive), std_dev > 0
#DIV/0!
Cause: Sample size = 1
Solution: Need at least 2 samples for t-distribution
#NUM!
Cause: Sample size < 1
Solution: Provide integer sample size ≥ 2
Notes
- Size parameter is truncated to integer if decimal
- Uses one-tailed t-distribution
- Result is half-width of confidence interval
- For full interval: mean ± CONFIDENCE.T result
- Excel 2010+ only - use CONFIDENCE in older versions
Compatibility
Available in: Excel 2010, Excel 2013, Excel 2016, Excel 2019, Excel 2021, Microsoft 365
Not available in: Excel 2007, Excel 2003, Excel XP
Content last reviewed: December 9, 2025
Update frequency: As needed
Excel versions tested: Excel 2010+