Confidence t function

This article describes the formula syntax and usage of the CONFIDENCE.T function in Microsoft Excel.

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

Syntax

CONFIDENCE.T(alpha,standard_dev,size)

The CONFIDENCE.T function syntax has the following arguments:

• Alpha     Required. 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     Required. The population standard deviation for the data range and is assumed to be known.

• Size     Required. The sample size.

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 truncated.

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

Example

Copy the example data in the following table, and paste it in cell A1 of a new Excel worksheet. For formulas to show results, select them, press F2, and then press Enter. If you need to, you can adjust the column widths to see all the data.

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