Syntax
ZTEST(array, x, [sigma])
| Parameter | Description |
|---|---|
| array | Parameter of the ZTEST function. |
| x | Parameter of the ZTEST function. |
| [sigma] | (Optional.) Parameter of the ZTEST function. |
Examples
Quality control check
Formula
=ZTEST(A2:A26, 75)
Returns the one-tailed p-value testing if the 25 samples in A2:A26 have a mean significantly greater than 75.
Known standard deviation
Formula
=ZTEST(B2:B101, 500, 50)
Tests whether the 100 observations differ from a population mean of 500, using the known population standard deviation of 50.
Checking if mean is below target
Formula
=1-ZTEST(C2:C51, 80)
Returns the probability that the sample mean is significantly less than 80 (the left-tail p-value).
Common Errors
#N/A
Returned if the array has no numeric values.
#VALUE!
Occurs if the hypothesized mean is non-numeric.
Tips
Migrate to Z.TEST
ZTEST is the compatibility function. Use Z.TEST in new spreadsheets for consistency with the modern function naming convention.
Understanding the output
A value close to 0 means the sample mean is much higher than the hypothesized mean. A value close to 1 means the sample mean is near or below the hypothesized mean.
Minimum sample size
While there is no hard minimum, the z-test assumes normality. For non-normal data, aim for at least 30 observations so the Central Limit Theorem can take effect.
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