The z-test functions are used to find values associated with z-test statistical analysis for large data samples, usually greater than 30, and where the variance is known. This section describes how to build visualizations using sample data to find the values of the z-test functions available in Qlik Sense. Please refer to the individual z-test chart function topics for descriptions of syntax and arguments.
Loading the sample data
The sample data used here is the same as that used in the t-test function examples. The sample data size would normally be considered too small for z-test analysis, but is sufficient for the purposes of illustrating the use of the different z-test functions in Qlik Sense.
Do the following:
- Create a new app with a new sheet and open that sheet.
In the data load editor, enter the following:
crosstable LOAD recno() as ID, * inline [
25|2 ] (delimiter is '|');
In this load script, recno() is included because crosstable requires three arguments. So, recno() simply provides an extra argument, in this case an ID for each row. Without it, Comparison sample values would not be loaded.
- Click l to load data.
Creating z-test chart function visualizations
Do the following:
In the data load editor, click ” to go to app view, and then click the sheet you created when loading the data.
The sheet view is opened.
- Click @ Edit sheet to edit the sheet.
- From Charts add a table, and from Fields add Type as a dimension.
Add the following expressions to the table as measures.
The resulting table for the z-test functions for the sample data will contain the following values:
|Type||ZTest Conf||ZTest Dif||ZTest Sig||ZTest Sterr||ZTest Z|
Creating z-testw chart function visualizations
The z-testw functions are for use when the input data series occurs in weighted two-column format. The expressions require a value for the argument weight. The examples here use the value 2 throughout, but you could use an expression, which would define a value for weight for each observation.
Examples and results:
Using the same sample data and number formatting as for the z-test functions, the resulting table for the z-testw functions will contain the following values:
|Type||ZTestw Conf||ZTestw Dif||ZTestw Sig||ZTestw Sterr||ZTestw Z|