ZTEST(ref,x[,stddev])
ZTEST returns the two-tailed probability of a z-test.
ref is the data set and x is the value to be tested.
stddev is optionally an assumed standard deviation.
Let us assume that the cells A1, A2, ..., A5 contain numbers 11.4, 17.3, 21.3, 25.9, and 40.1. Then
ZTEST(A1:A5,20) equals 0.254717826.
CONFIDENCE, NORMDIST, NORMINV, NORMSDIST, NORMSINV, STANDARDIZE.