In Excel 2010, the CONFIDENCE() function was replaced with the CONFIDENCE.NORM() function, and the CONFIDENCE.T() function was added to increase the accuracy of the results. To ensure the backward compatibility of CONFIDENCE.NORM() and CONFIDENCE.T(), the CONFIDENCE() function is still available.
Definition. This function returns a value used to create a confidence interval for the expected value of a random variable. The confidence interval is a range of values. The 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 delivery times for products ordered through the mail, x ± CONFIDENCE.NORM() is ...