How to Run a Z-Test with Z.TEST in Excel

Use Z.TEST to check whether a sample average is above a benchmark — and turn its one-tailed result into a two-tailed p-value.

You will learn to

• Run a z-test with the sample’s own SD
• Run it with a known population SD
• Convert the result to a two-tailed p-value

How it works

Z.TEST returns the one-tailed p-value for "is the true average of this data greater than x?". Give it the data range, the benchmark and, if you know it, the population standard deviation; without sigma it uses the sample standard deviation.

It only looks at one direction. For a two-tailed test — "is the average different from x, higher or lower?" — use =2*MIN(Z.TEST(data,x,sigma),1-Z.TEST(data,x,sigma)). A small p-value means the sample average would be surprising if the true average were x.

=Z.TEST(B2:B13,70,10)