2.1.1030 Part 1 Section 188.8.131.520, STDEVA
a. The standard maps x to the sample mean and n to the sample size.
Office maps x-bar to the sample mean, n to the sample size and x to a sample value.
b. The standard does not specify what happens if size is less than or equal to one.
Office returns #DIV/0! if sample size is less than or equal to one.