## Description

The Excel CONFIDENCE.NORM() function is used to get the confidence interval for a population mean, using a normal distribution. The confidence interval is a range of values. Your sample mean, x, is at the center of this range and the range is x ± CONFIDENCE.NORM.

Version: Excel 2013

Syntax

`CONFIDENCE.NORM(alpha,standard_dev,size)`

Parameters

Name Description Data Type Required/
Optional
Alpha 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. number Required
A standard_dev The population standard deviation for the data range and is assumed to be known. number Required
Size The sample size. number Required

Remarks :

• 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.
• If we assume alpha equals 0.05, we need to calculate the area under the standard normal curve that equals (1 - alpha), or 95 percent. This value is ± 1.96. The confidence interval is therefore:

Example : Excel CONFIDENCE.NORM() function
The following worksheet shows confidence interval for a population mean. In other words, the confidence interval for the underlying population mean for travel to work equals 30 ± 0.692952 minutes, or* 29.3 to 30.7 minutes.

Sample Data Description
0.05 Significance level
2.5 Standard deviation of the population.
50 Sample size.

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Source:http://www.w3resource.com/excel/excel-confidence-dot-norm-function.php