# ZTEST

Formulas / ZTEST
Calculate the one-tailed probability-value of a z-test.
`Z.TEST(array,x,[sigma])`
• array - The array or range of data that represents the sample set for which you want to perform the z-test.
• x - The hypothesized value of the population mean.
• sigma - The known population standard deviation. If omitted, the sample standard deviation is used.

## Examples

• `=ZTEST(A2:A11,4)`

The ZTEST function in Sourcetable is used to test the deviation of a dataset from a hypothesized population mean. For example, let's assume we have a data set of 10 values: A2:A11. We can use the ZTEST function to calculate the one-tailed probability-value of a z-test for the data set at the hypothesized population mean of 4. This will return the probability-value of 0.090574.

• `=2 * MIN(ZTEST(A2:A11,4), 1 - ZTEST(A2:A11,4))`

We can also use the ZTEST function to calculate the two-tailed probability-value of a z-test. To do this, we use the same data set as in example 1, but we enter the preceding formula into the cell. This will return the two-tailed probability-value of 0.181148.

• `=ZTEST(A2:A11,6)`

We can also use the ZTEST function to calculate the one-tailed probability-value of a z-test for the data set at a different hypothesized population mean. For example, if we hypothesize that the population mean is 6, use this example, and will return the probability-value of 0.863043.

## Summary

The ZTEST function is a statistical tool that calculates the probability that the sample mean is greater than the average of observations in the data set. It offers improved accuracy compared to other tests.

• ZTEST is a Sourcetable function that may provide improved accuracy in future versions of Excel.

What is the ZTEST function?
The ZTEST function is a statistical tool used to calculate the one-tailed probability-value of a z-test. It determines the probability that the sample mean would be greater than the average of observations in the data set.
What is the difference between the old and new ZTEST functions?
The new Z.TEST function may provide improved accuracy.
Is the old ZTEST function still available?
Yes, the ZTEST function is still available for backward compatibility.
What happens if the array argument is empty?
The ZTEST function throws a #N/A error if the array argument is empty.
What does ZTEST represent?
ZTEST represents the probability that the sample mean would be greater than the observed value AVERAGE(array).