The CONFIDENCE.NORM function returns the confidence interval for a population mean, using a normal distribution. Your sample mean, x, is at the center of this range and the range is x ± CONFIDENCE.NORM.

For example, if x is the sample mean of the length of major league baseball games, x ± CONFIDENCE.NORM is a range of population means. For any population mean, μ0, in this range, the probability of obtaining a sample mean further from μ0 than x is greater than alpha; for any population mean, μ0, not in this range, the probability of obtaining a sample mean further from μ0 than x is less than alpha. In other words, assume that we use x, standard_dev, and size to construct a two-tailed test at significance level alpha of the hypothesis that the population mean is μ0. Then we will not reject that hypothesis if μ0 is in the confidence interval and will reject that hypothesis if μ0 is not in the confidence interval. The confidence interval does not allow us to infer that there is probability 1 – alpha that the next game will longer than time that is in the confidence interval.

CONFIDENCE.NORM takes 3 required arguments and no optional arguments:

Syntax: CONFIDENCE.NORM(alpha, standard_dev, size)

#1)
Using the CONFIDENCE.NORM function:
#2)
The arguments for the CONFIDENCE.NORM function are:
Argument Required? Description
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.
#3)
A few more things:
If any argument is nonnumeric, CONFIDENCE.NORM returns the #VALUE! error value.
If alpha ≤ 0 or alpha ≥ 1, CONFIDENCE.NORM returns the #NUM! error value.
If standard_dev ≤ 0, CONFIDENCE.NORM returns the #NUM! error value.
If size is not an integer, it is truncated.
If size < 1, CONFIDENCE.NORM returns the #NUM! error value.

Summary

The CONFIDENCE.NORM function the confidence interval for a population mean, using a normal distribution.
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