# TTest1\_dif - script and chart function

TTest1\_dif() returns the aggregated student's t-test mean difference for a series of values.

This function applies to one-sample student's t-tests.

If the function is used in the 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:

TTest1\_dif (value)

Return data type: numeric

Arguments:

* value: The samples to be evaluated. If a field name for the sample values is not provided in the load script, the field will automatically be named Value.

Limitations:

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

Example:

`TTest1_dif( Value )`

## Learn more

* [Creating a typical t-test report](https://help.qlik.com/en-US/qlikview/September2026/Subsystems/Client/Content/QV_QlikView/ChartFunctions/StatisticalTestFunctions/ttest/ttest_t_example.htm)