A span is Q's term for groups of categories (e.g., Male, Female, and Income in the example below). You can modify and create Spans on banners in the usual ways. You can also automatically place spans above questions by right-clicking and selecting Create Span.
When using Column Comparisons, Q only compares columns within a span by default. However, sometimes you may have Banners where you want to compare data across spans (for spans created by crossing a grid or multi question by another question please see below). You can easily change some settings in the statistical assumptions to allow for testing across spans. Then you can go to a table like this that is tested within span:
to one tested across spans:
- A crosstab with multiple columns, showing spans. (crosstabs using grid/multi questions see below)
- Where the focus is on comparing dates within a Banner, see the Significance testing section on Banners.
Method - Allow Q to test across spans
You have some options as to how to do this. You can:
- You can always Delete spans on the Banner to test across spans.
- Or you will need to NOT recycle the letters for each span to allow Q to test across spans. To do this on a project level, go to the Edit > Project Options > Customize > Statistical Assumptions > Column Comparison section. Otherwise, right click on a column header in your banner and go to the Table Options > Statistical Assumptions > Column Comparison section. Uncheck Recycle column letters.
Method - Review other testing settings
- If you are applying Multiple comparison correction, confirm whether you want to take into account only columns Within row and span or not.
- Confirm how you would like to treat Overlaps in the data, by default respondents present in both columns being tested are removed from the test. See Overlaps on our wiki for more info.
Method - Specify the columns to be tested
This example tests All Columns, but you can use other settings per How to Specify Columns to be Compared in a Table. Note these settings will be applied to ALL TABLES that use this question.
If you are using Q version 5.12.4 or lower or if you are editing Project Options:
- Click OK to close the options.
- Right click on a column header again and select Comparisons.
- Select the option for how you'd like your columns tested, in this example, select All columns and click OK.
If you are using a Q version after 5.12.4:
- At the bottom of the Column Comparisons tab you'll see a section for this specific question - Compare. For this example select All columns and click OK.
Grid/Multi Crosstab Method
Because grid/multi crosstabs are structured differently than nested banners, the built-in column comparisons testing will always test within the spans. You will need override the built-in significance tests. using a rule on the table(s). Select Automate > Browse Online Library > Significance Testing in Tables - Independent Samples Column Means and Proportions Tests. There you can select Set column comparisons and enter the desired column comparisons.