## Excel ZTEST Function ### Description

The Excel ZTEST function returns the one-tailed P-value of a z-test which is useful for various analyses. Based on the given hypothesized population mean, x, ZTEST function returns the probability that the sample mean would be greater than the observed sample mean.

Note: This function has been replaced with one or more functions that may provide improved accuracy after Excel 2010 version. This function is still can be available but considering it may be not available in the future, you should better study to use the new function from now.

Formula syntax

ZTEST(array,x,[sigma])

Arguments

 array: Required, the array or range of the data against which to test x. x: Required, the value used to test. sigma: Optional, represents to use the population’s standard deviation if this is known. If it is omitted, the sample standard deviation is used.

### Returns

ZTEST function returns a numeric value.

### Remarks

1. ZTEST represents the probability that the sample mean would be greater than the observed mean AVERAGE(array), when the underlying population mean is μ0. From the symmetry of the normal distribution, if AVERAGE(array) < x, ZTEST returns a value greater than 0.5.

2. ZTEST is calculated as follows

• when sigma is known: • when sigma is omitted: Where x is the sample mean AVERAGE(array), and n is COUNT(array), and s is the sample standard deviation STDEV(array).

### Errors

1. #VALUE! error – Occurs when the x or sigma is not a numeric value.

2. #NUM! error – Occurs when sigma = 0.

3. #N/A! error – Occurs when array is empty.

4. #DIV/0! error – Occurs when array contains only one value, or sigma is omitted and the standard deviation of the supplied array is 0.

### Version

Excel 2007 and earlier versions

### Usage and Examples

Basic usage

To get the one-tailed probability value of a z-test for the data in range B3:B9 with a hypothesized population mean of 6, please use the formula as this:

=ZTEST(B3:B9,6)

Press Enter key to get the result. #### Other Functions:

• Excel POISSON Function
The Excel POISSON function returns the Poisson distribution which is used to predict the number of events occurring over a specific time.

• Excel WEIBULL Function
The Excel WEIBULL function returns the Weibull probability density function or Weibull cumulative distribution for a supplied set of parameters.

• Excel Z.TEST Function
The Excel Z.TEST function (2010) returns the one-tailed P-value of a z-test which is useful for various analyses.

• Excel F.DIST Function
The Excel F.DIST function returns the F probability distribution which is usually used to measure the degree of diversity between two data sets.

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