Detecting outliers with Mandel’s h and k statistics with XLSTAT
Dataset for testing differences between samples with Mandel's statistics
An Excel sheet with both the data and the results can be downloaded by clicking here.
Four samples have been obtained from two different distribution: 3 with a normal distribution with mean 0 and variance 2 and one with a normal distribution with mean 0 and variance 5 .We suppose that each sample is related to the results of a laboratory. We wish to test if there are differences between laboratories' results.
Goal of this tutorial
We would like to detect if means and variances are homogeneous using the h and k statistics of Mandel. You can find some detail on these statistics here.
Setting up a h and k Mandel's statistics analysis
To start the Madel's h and k statistics go to the menu Testing outliers / Mandel's h and k statistcs.
In the General tab, select the data. Four columns should be selected with the option one column per group.
When ready click on OK.
Results of a h and k Mandel's statics
In the following table, we can see the h and k statistics for each laboratory.
In the following graphic, the h statistics are displayed together with the critical value. We can see that none of the values are outside the critical interval.
The same graphic is available for the k statistic. It also shows that none of the laboratory obtain an outlying k statistic.
We have shown that there is no outlying laboratory in this study.
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