# Z.TEST Function

The Z.TEST function is one of the statistical functions. It is used to return the one-tailed P-value of a z-test. For a given hypothesized population mean, x, Z.TEST returns the probability that the sample mean would be greater than the average of observations in the data set (array) — that is, the observed sample mean.

The Z.TEST function syntax is:

Z.TEST(array, x [, sigma])

where

array is the range of numeric values against which to test x.

x is the value to test.

sigma is a population standard deviation. This is an optional argument. If it is omitted, the sample standard deviation is used.

The values can be entered manually or included into the cell you make reference to.

To apply the Z.TEST function,

1. select the cell where you wish to display the result,
2. click the Insert function icon situated at the top toolbar,
   or right-click within a selected cell and select the Insert Function option from the menu,
   or click the icon situated at the formula bar,
3. select the Statistical function group from the list,
4. click the Z.TEST function,
5. enter the required arguments separating by commas or select a range of cells with the mouse,
6. press the Enter button.

The result will be displayed in the selected cell.