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ZTEST Function

Excel 2007+

Summary

The ZTEST function performs a one-tailed z-test to determine the probability that the sample mean is greater than a hypothesized population mean. It calculates the p-value associated with a z-statistic for hypothesis testing.

Syntax

ZTEST(array, x, [sigma])

Parameters

Parameter	Type	Required	Description
array	`Number array`	Yes	The array or range of sample data for testing
x	`Number`	Yes	Hypothesized population mean value
sigma	`Number`	No	Known population standard deviation (sample std dev used if omitted)

Using the ZTEST Function

ZTEST is used in statistical hypothesis testing to assess whether a sample mean significantly differs from a hypothesized population mean. It returns the one-tailed p-value, helping researchers and analysts determine statistical significance in their data analysis.

Common ZTEST Examples

Basic One-Tailed Z-Test

=ZTEST(A2:A11,4)

Calculates one-tailed p-value testing if sample mean > 4 (result: 0.090574)

Two-Tailed Z-Test Formula

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

Converts one-tailed result to two-tailed p-value (result: 0.181148)

Test with Hypothesized Mean of 6

=ZTEST(A2:A11,6)

Tests if sample mean > 6 using sample std dev (result: 0.863043)

Frequently Asked Questions

#N/A error value is returned when no data is provided

Use: 2 * MIN(ZTEST(array,x,sigma), 1 - ZTEST(array,x,sigma))

Use known population sigma for accuracy; omit for sample standard deviation

Common Errors and Solutions

#N/A Error

Cause: Empty array or range provided

Solution: Ensure array contains numeric data

#VALUE! Error

Cause: Non-numeric values in array or invalid parameters

Solution: Verify all inputs are numbers

Unexpected p-value > 0.5

Cause: Sample mean less than hypothesized value

Solution: This is normal due to one-tailed test nature

Notes

Legacy function - consider Z.TEST for improved accuracy
Returns probability sample mean > observed mean when population mean = x
If sample mean < x, result > 0.5 due to normal distribution symmetry
Excel 2007+ compatibility

Compatibility

Available in: Excel 2007, Excel 2010, Excel 2013, Excel 2016, Excel 2019, Excel 2021, Microsoft 365

Not available in: Excel 2003 and earlier

Content last reviewed: December 9, 2025
Update frequency: As needed
Excel versions tested: Excel 2007+