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



The CONFIDENCE.T function syntax has the following arguments (argument: A value that provides information to an action, an event, a method, a property, a function, or a procedure.):

  • 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.


  • 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.
Applies to:
Excel 2010, Excel Web App