Confidence Function in Excel returns the value that you can use to construct the confidence interval for a population mean. Confidence Function uses a Normal Distribution to calculate a confidence value.
Syntax of CONFIDENCE Function in Excel:
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.
How to Calculate Confidence interval in excel?
The output value of confidence 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 Function in Excel:
- Confidence value is calculated by passing alpha, standard deviation and population size to the CONFIDENCE 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
- 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
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