When statistical tests are conducted on tables containing share statistics (e.g., % Column Share), the tests are conducted using the averages, not the share statistics. This can lead to counter-intuitive results when reporting the shares. This page describes how to get Displayr to instead test differences between the shares.
Example of the problem
In the table below on the left, for example, the automatic statistical testing shows that Pepsi is significantly higher amongst the heavy consumers than the light consumers, but the actual numbers on the table show the opposite conclusion. The table on the right shows the averages, from which we can see that the average is higher for Pepsi amongst Heavy consumers.
Requirements
A numeric - multi variable set in your data set.
Please note these steps require a Displayr license.
Method
The solution to the problem is to transform the data, so that the Average on the table is proportional to the % Column Share:
- Select a numeric - multi variable set from the Data Sources tree.
- Compute a new variable set that contains the share computed for each case. From the toolbar, go to Anything
> Data > Variables > New > Ready-Made New Variable(s) > Case-Level Shares.
- Select the original variables in the Data Sources tree.
- Hover and click + > Ready-Made New Variables > Sum.
- Tag the newly-created variable as a weight by ticking Usable as a weight from Data > Properties in the object inspector.
- Select the table and apply the weight via Data > Filters & Weight > Weight.
The Average and % Column Share on the tables will now coincide, and the statistical tests now, as a consequence, can be interpreted as testing differences in % Column Share.