The CONFIDENCE.T function returns the confidence interval for a population mean, using a Student’s T-distribution.
- This function was introduced in Excel 2010 and so is not available in earlier versions.
- CONFIDENCE.T and CONFIDENCE.NORM functions replace the CONFIDENCE function included in earlier versions of Excel.
|alpha||Specifies the name of a parameter
|standard_dev||The standard deviation of the population|
|size||The population sample size|
|7||=CONFIDENCE.T(A2,A3,A4)||0.496054||Confidence interval, based on Student’s T-distribution, for the mean of a population based on a sample size of 100, with a 5% significance level and a standard deviation of 2.5|
Usage note: To calculate the confidence interval for a population mean, the returned CONFIDENCE value must then be added to, and subtracted from, the sample mean. I.e. for the sample mean :
In the example above, the CONFIDENCE.T function is used to calculate the confidence interval, with a significance of 0.05 (confidence level of 95%), for the travel time to work for a sample population of 100 people. The sample mean is 30 minutes and the standard deviation is 2.5 minutes.
Therefore, the confidence interval is , which is equal to a drive time of 30 ± 0.496054 minutes, or 29.5 to 30.5 minutes.
Common Function Error(s)
|Problem||What went wrong|
|#VALUE!||Occurs if any of the supplied arguments are non-numeric|
|#NUM!||Occurs if either:
|#DIV/0!||Occurs if the supplied size argument = 1|
In statistics, the confidence interval is the range of values into which a population parameter is likely to fall, for a given probability.
For example, for a given population and a probability of 95%, the confidence interval is the range, in which a population parameter is 95% likely to fall.
Note that the accuracy of the confidence interval relies on the population having a normal distribution.
See Wikipedia for more information on confidence interval.