This article describes how to test for significant differences between two questions. For example, supposeyou want to test for differences between two questions: "Have you ever eaten at the following restaurants" and "Have you ever considered eating at the following restaurants".
To do so, they must first be combined into a binary grid like the one below:
Requirements
Two categorical variables with the same categories.
Method
Combining the Q3 and Q4 into a single variable
In this example, we will be using two variables, Q3 and Q4. Before beginning, we will create duplicate copies of each variables:
- From the Data Sets tree, select variables Q3 and Q4
- Right-click the highlighted area and select Duplicate.
The two duplicates are still highlighted. - Right-click one of the highlighted variables and select Combine
Remove unnecessary categories
The category None of these is a category of the Consider Eating At... variable but not the Ever Eating at... variable so we will remove it. We will also remove the Other fast food category because it is non-specific.
- Right-click the combined variable, and from the menu, select Reset > Table Categories
- Select all the categories, and then Contol-Click to unselect the None of these and Other fast food categories
- Right-click the highlighted area and select Combine
Change the variable names
Each variable names is repeated twice so it is hard to tell whether they came from the "Have you ever eaten at..." questions or the "Have you even considered eating at..." question. We will use Wildcards to make the renaming process a little easier. Click here for more information on how to use Find and Replace in Displayr
- Select the all the variables, right-click and select Split
- Select the first set of variables
- In the toolbar, type * in the search box and then click This Document
- On the left, select ADVANCED and check the Use Wildcard box
- Select Replace and in the Replace with box and type Eaten at ${0}
- Under FIND IN, check the Only search selected items box
- Click Replace All
- Select the second set of variables
- In the Replace with box, type Considered ${0}
- Click Replace All
Next we will get rid of the number "1" at the end of these variable names - In the search box at the top of the screen, replace the * with 1
- Remove whatever is in the Replace with box
- Click Replace All
Finalize the new variable
- Select all the renamed categories, right-click and select Combine
- In the Object Inspector, ensure the Structure is set to Binary - Grid
- Drag the variable onto the page
Perform a statistical test
- In the Object Inspector, select Table > Properties > Significance > Compare Columns
Next
How to Compare Significant Differences Between Columns