CONFIDENCE.NORM Function in Excel

CONFIDENCE.NORM Function in Excel returns the value that you can use to construct the confidence interval for a population mean.  CONFIDENCE.NORM Function uses a Normal Distribution to calculate a confidence value.

 

Syntax of CONFIDENCE.NORM Function in Excel:

CONFIDENCE.NORM( alpha, standard_dev, size )

where the arguments are as follows:

  • alpha – probability value between 0 and 1, it is also known as significance level (= 1 – confidence level). Usually alpha will be 0.05 which equates to a confidence level of 95%.
  • standard_dev – The standard deviation of the population.
  • size –              The population sample size.

The output value of CONFIDENCE.NORM function i.e. confidence value should be added to and subtracted from the sample mean to calculate the confidence interval.
Confidence Interval = Sample Mean ±   CONFIDENCE Value

Example of CONFIDENCE.NORM Function in Excel:

Formula

CONFIDENCE.NORM Function in Excel 1

  • Confidence value is calculated by passing alpha, standard deviation and population size to the CONFIDENCE.NORM Function in Excel as shown in First example.
  • Sample mean is calculated in the second row.

Now we need have mean and confidence value. So we need to calculate the confidence interval using formula

Confidence Interval = Sample Mean ±   CONFIDENCE Value
  • Sample mean+ confidence value is called upper bound of confidence interval. Which is calculated in Third row as shown above
  • Sample mean – confidence value is called lower bound of confidence interval Which is calculated in Fourth row as shown above

So the result will be

Result

CONFIDENCE.NORM Function in Excel 2

95 % confidence interval of sample mean for the above set of values is 55.6667± 4.7116 which ranges from 50.9554 to 60.3778

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