# ZTest\_conf Script and chart function

ZTest\_conf() returns the aggregated z value for a series of values.

If the function is used in the data load script, the values are iterated over a number of records as defined by a group by clause.

If the function is used in a chart expression, the values are iterated over the chart dimensions.

Syntax:

ZTest\_conf(value[, sigma[, sig]])

Return data type: numeric

Arguments:

Arguments

| Argument | Description |
| --- | --- |
| value | The sample values to be evaluated. A population mean of 0 is assumed. If you want the test to be performed around another mean, subtract that mean from the sample values. |
| sigma | If known, the standard deviation can be stated in sigma. If sigma is omitted the actual sample standard deviation will be used. |
| sig | The two-tailed level of significance can be specified in sig. If omitted, sig is set to 0.025, resulting in a 95% confidence interval. |

Limitations:

Text values, NULL values and missing values in the expression value will result in the function returning NULL.

Example:

` ZTest_conf(Value-TestValue)  `

## Learn more

* [Examples of how to use z-test functions](https://help.qlik.com/en-US/cloud-services/Subsystems/Hub/Content/Sense_Hub/ChartFunctions/StatisticalTestFunctions/ztest/ztest-example.htm)