When you select one or more cells in the table and select from the Object Inspector
> Appearance > Significance menu, an expert system in Displayr determines the test that you most likely want and conducts this test. This is referred to as a planned test because, unlike the automatic tests shown in tables, the relationship is tested as if it were planned before the research was conducted, so no correction is made for multiple comparisons.
The output below, for example, shows a significant difference between the typical levels of coffee and cola consumption.
As shown in the null hypothesis, the test actually checks whether the median is different (i.e., it does not compare averages). Further, in this example, the test was deemed significant because the p-value was less than or equal to 0.1 (by default, it is 0.05, but can be changed by changing the Overall significance level).
Sometimes a result will be shown as being significant when you press , but it will not be shown as significant in the table. This is generally because multiple comparison corrections have been applied when highlighting cells as significant, whereas the results obtained by pressing
contain no corrections (see Multiple Comparisons (Post Hoc Testing)).
Displayr works out which test to conduct by taking into account the structure of the data (e.g., categorical, numeric, paired, etc. - see Tests Of Statistical Significance and the settings in Statistical Assumptions.
Warnings
- It is always important to read the precise wording of the Null hypothesis, as it will indicate what the result actually means.
- When you press
no, Multiple Comparisons Correction is applied. Thus, a cell that is not shown as being significant on a table may be shown as being significant when