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:**

**Formula**

- 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

**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**

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**