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The ZTEST function in Google Sheets returns the one-tailed probability-value of a z-test. It is used to determine whether a sample mean is significantly different from a hypothesized value, assuming a known population standard deviation. This function is typically used in hypothesis testing and statistical analysis.


Use the ZTEST formula with the syntax shown below, it has 2 required parameters and 1 optional parameter:

=ZTEST(data, value, [standard_deviation])
  1. data (required):
    The range or array of sample data for which to perform the z-test.
  2. value (required):
    The hypothesized value of the population mean.
  3. standard_deviation (optional):
    Optional. The known population standard deviation. If omitted, the sample standard deviation will be used.


Here are a few example use cases that explain how to use the ZTEST formula in Google Sheets.

Testing a sample mean

You can use the ZTEST function to test whether a sample mean is significantly different from a hypothesized value, assuming a known population standard deviation.

Comparing two sample means

The ZTEST function can be used to compare two sample means to determine if they are significantly different from each other, assuming a known population standard deviation.

Quality control

ZTEST can be used in quality control to determine if a sample of products is significantly different from the expected value, assuming a known population standard deviation.

Common Mistakes

ZTEST not working? Here are some common mistakes people make when using the ZTEST Google Sheets Formula:

Using the wrong type of test

ZTEST should be used when the population standard deviation is known. If it is not known, you should use the TTEST function instead.

Not specifying the correct value for the hypothesized mean

Make sure you are using the correct value for the hypothesized population mean. If you are not sure what value to use, consult with a subject matter expert.

Not using a large enough sample size

In order for the results of a z-test to be reliable, you need a large enough sample size. If your sample size is too small, the results may not be significant even if there is a real difference between the sample mean and the population mean.

The following functions are similar to ZTEST or are often used with it in a formula:


    The TTEST formula is a statistical formula used to determine the probability of two sample means being equal. It is commonly used in hypothesis testing to determine if there is a significant difference between two sets of data. The formula returns the probability value associated with a t-test, which can be used to determine if the null hypothesis should be rejected or not.


    The NORMDIST function in Google Sheets calculates the normal distribution for a specified value, mean, and standard deviation. It returns the probability of a value occurring within a specified range of a normal distribution. It is commonly used in statistics, finance, and science to analyze data and make predictions.


    The STDEV function calculates the standard deviation of a set of numbers. It measures the amount of variation or dispersion of a set of values from the average (mean) value. It is commonly used in statistics to determine the spread of a data set. The values can be supplied as individual cells, ranges, or constants.


    The AVERAGE function calculates the average (arithmetic mean) of the values passed to it. It is commonly used to find the average of a range of cells containing numerical data.

Learn More

You can learn more about the ZTEST Google Sheets function on Google Support.