By default, **Column Comparisons** in Q 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 project or specific tables in a project.

## Modifying the significance levels for the entire project

**Edit > Project Options > Customize > Statistical Assumptions**.- 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.

## Modifying the significance levels for a particular table

This is exactly the same as with Modifying the significance levels for the entire project, except that:

- First select the tables you wish to modify in the Report Tree.
- Select
**Edit > Table Options > Statistical Assumptions**. - If you need to modify any of the
**Column letter**settings, you will first need to go into**Project Options > Statistical Assumptions**to review the settings there (as the settings in Table Options show differences from Project Options), and, if necessary, copy the contents of the**Column letters**cells to paste into Table Options.

## 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 **menus.

The footers need to be updated to show that you have conducted one-tailed tests. This is done as follows:

- Select all the tables where you are conducting one-tailed testing (select all the tables in the project if you are applying one-tailed testing to the entire project).
**Edit > Table Options > Footer**- Replace the contents of the
**Significance Testing > Text**with whatever you wish. For example,`One-tailed test at 90% level of confidence`.

## Next

How to Show Statistical Significance in Q

How to Modify Significance Tests

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