TTest_dif() is a numeric function that returns the aggregated student's t-test mean difference for two independent series of values.
This function applies to independent samples student's t-tests.
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:
TTest_dif (grp, value [, eq_var] )
Return data type: numeric
Arguments:
| Argument | Description |
|---|---|
| value | The sample values to be evaluated. The sample values must be logically grouped as specified by exactly two values in group. If a field name for the sample values is not provided in the load script, the field will automatically be named Value. |
| grp | The field containing the names of each of the two sample groups. If a field name for the group is not provided in the load script, the field will automatically be given the name Type. |
| eq_var | If eq_var is specified as False (0), separate variances of the two samples will be assumed. If eq_var is specified as True (1), equal variances between the samples will be assumed. |
Limitations:
Text values, NULL values and missing values in the expression value will result in the function returning NULL.
Examples:
TTest_dif( Group, Value )
TTest_dif( Group, Value, false )