2.1.1063 Part 1 Section 126.96.36.1996, ZTEST
a. The standard does not specify how function arguments map to formula variables.
Office maps x-bar to sample mean and µ_0 to argument test-value.
b. In the standard, there is no restriction on the value of sigma.
In Office, if sigma is less than or equal to 0, then #NUM! is returned.