Syntax
Z.TEST(array, x, [sigma])
| Parameter | Description |
|---|---|
| array | Parameter of the Z.TEST function. |
| x | Parameter of the Z.TEST function. |
| [sigma] | (Optional.) Parameter of the Z.TEST function. |
Examples
Testing if batch average meets spec
Formula
=Z.TEST(A2:A31, 50)
Returns the one-tailed p-value testing whether the 30 measurements in A2:A31 come from a population with mean 50. Uses the sample standard deviation since sigma is omitted.
With known population std dev
Formula
=Z.TEST(B2:B51, 100, 15)
Returns the one-tailed p-value testing if the 50 values in column B come from a population with mean 100 and known standard deviation 15.
Two-tailed z-test
Formula
=2*MIN(Z.TEST(C2:C41, 200), 1-Z.TEST(C2:C41, 200))
Converts the one-tailed result to a two-tailed p-value by doubling the smaller tail probability.
Common Errors
#N/A
Returned if the array is empty or contains no numeric values.
#VALUE!
Occurs if x (the hypothesized mean) is non-numeric.
Tips
One-tailed by default
Z.TEST returns a one-tailed p-value (the probability that the sample mean is greater than or equal to what was observed). For a two-tailed test, use =2*MIN(Z.TEST(...), 1-Z.TEST(...)).
Sigma is optional
If you omit the third argument, the sample standard deviation is used. Only specify sigma when you know the true population standard deviation.
Z-test vs t-test
Z.TEST is appropriate when the population standard deviation is known or the sample size is large (n > 30). For small samples with unknown sigma, use T.TEST instead.
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