# ZTEST

Returns the two-tailed P-value of a z-test. The z-test generates a standard score for x with respect to the data set, array, and returns the two-tailed probability for the normal distribution. You can use this function to assess the likelihood that a particular observation is drawn from a particular population.

**Syntax**

**ZTEST**(**array**,**x**,sigma)

**Array** is the array or range of data against which to test x.

**X** is the value to test.

Sigma is the population (known) standard deviation. If omitted, the sample standard deviation is used.

**Remarks**

- If array is empty, ZTEST returns the #N/A error value.
- ZTEST is calculated as follows:

**Example**

`ZTEST({3,6,7,8,6,5,4,2,1,9},4)`

equals 0.090574