By default, Column Comparisons in Displayr are all two-tailed. However, they can be converted to one-tailed tests by modifying the significance levels. This modification can either be done for an entire document or specific tables in a document.
Modifying the significance levels for the entire document
- Select a table and on the right click Properties > APPEARANCE > Significance > Advanced > Significance Levels.
- Enter a value into the Overall significance level that is double your desired level. For example, if you are wanting to do a one-tailed test at the 0.05 level (95% level of confidence), enter 0.10 (i.e., 2 * 0.05) into the box.
- Make appropriate adjustments via cutting and pasting of the Column Letters column in Significance levels and appearance, and, if necessary, adding or deleting new rows by pressing the green + and red - buttons.
- Select Set as Default.
Modifying the significance levels for a particular table
This is exactly the same as with Modifying the significance levels for the entire document, except that:
- First select the tables or pages where the tables are that you wish to modify in the Pages section.
- Select Properties > APPEARANCE > Significance > Advanced > Significance Levels.
- Select Apply to Selection.
Multiple comparison corrections
Generally one-tailed tests are conducted in situations where there are clear a priori hypotheses regarding the likely results. In such situations it may be advisable to turn off any Multiple Comparison Corrections in the Statistical Assumptions > Column Comparisons menu.