# CONFIDENCE.T

Returns the confidence interval for a population mean, using a Student's t distribution.

## Syntax

CONFIDENCE.T(alpha,standard_dev,size)


### Parameters

Term Definition
alpha The significance level used to compute the confidence level. The confidence level equals 100*(1 - alpha)%, or in other words, an alpha of 0.05 indicates a 95 percent confidence level.
standard_dev The population standard deviation for the data range and is assumed to be known.
size The sample size.

## Return value

Returns the confidence interval for a population mean, using a Student's t distribution.

## Remarks

• If any argument is nonnumeric, CONFIDENCE.T returns the #VALUE! error value.

• If alpha ≤ 0 or alpha ≥ 1, CONFIDENCE.T returns the #NUM! error value.

• If standard_dev ≤ 0, CONFIDENCE.T returns the #NUM! error value.

• If size is not an integer, it is rounded.

• If size equals 1, CONFIDENCE.T returns #DIV/0! error value.

• This function is not supported for use in DirectQuery mode when used in calculated columns or row-level security (RLS) rules.

## Example

Formula Description Result
= CONFIDENCE.T(0.05,1,50) Confidence interval for the mean of a population based on a sample size of 50, with a 5% significance level and a standard deviation of 1. This is based on a Student's t-distribution. 0.284196855