# How to Specify Comparisons for ANOVA-Based Tests

When Column Comparisons are specified on a table a number of the **Multiple comparisons correction** methods that can be selected for **Column comparisons** in Statistical Assumptions make stringent assumptions about the relationship between the columns being tested. In particular, the ANOVA-Based Column Comparison corrections all assume that the columns are not overlapping (i.e., reflect independent samples). Where this assumption is not met, Q will return an error message.

## Specifying comparisons for most ANOVA-Based Column Comparisons

With the exception of Dunnett’s Pairwise Multiple Comparison , the ANOVA-Based Column Comparison corrections require non-overlapping columns. In practice, this generally means there is a need to removed NETs from a comparison. This can be done by either right-clicking on a NET category and selecting **Hide**, or, by creating a Span which excludes the NET (as when a Span is created, Q conducts the comparison using only within the spans). The following two images demonstrate the alternative ways of setting up the data appropriately.

## Specifying comparisons for Dunnett’s Pairwise Multiple Comparison

Dunnett’s Pairwise Multiple Comparison tests each category against one specific category of interest (e.g., new products are compared to a current product). It is set up by:

- Removing the NET category (as in the second example above).
- Removing and/or re-ordering categories so that the category of interest appears in the first column.
- Right-clicking on the columns and selecting
**Comparisons**and entering appropriate comparisons. For example:`A/B, A/C, A/D, A/E, A/F, A/G, A/H, A/I`.