The CONFIDENCE.NORM function returns the confidence interval for a population mean, using a normal distribution.
- This function was introduced in Excel 2010 and so is not available in earlier versions.
- CONFIDENCE.NORM and CONFIDENCE.T functions replace the CONFIDENCE function included in earlier versions of Excel.
|alpha||The significance level used to compute the confidence level
|standard_dev||The standard deviation of the population|
|size||The population sample size|
|7||=CONFIDENCE.NORM(A2,A3,A4)||0.489991||Confidence interval for a population mean|
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.NORM 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 ± 0.489991 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:
In statistics, the confidence interval is the range of values into which a population parameter is likely to fall, for a given probability. That is, a sample mean (x) is at the center of the range and the range is x ± CONFIDENCE.NORM.
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.