(This dialog is only available for CBC Advanced Design Module users and for CVA.)
Introduction
This area displays any current prohibitions in place for your project. It also lets you specify advanced prohibitions (if you are licensed with the Advanced Design Module or CVA software), including:
•n-way within-concept prohibitions
•n-way between-concept prohibitions
Before continuing, we should define within- vs. between-concept prohibitions.
Within-Concept Prohibition: If you want to prohibit a certain combination of attribute levels from appearing within the same product concept, that is a within-concept prohibition. For example, we may wish to prohibit the combination [Brand A, Green] from occurring.
Between-Concept Prohibition: If you want to prohibit which product concepts may be placed in competition with one another within the same conjoint task, this is a between-concept prohibition. For example, we may wish to prohibit a [Brand A, Green] product from ever appearing in competition with a [Brand A, Red] product within the same conjoint task.
Prohibitions are sometimes quite damaging to design efficiency. We strongly suggest avoiding prohibitions whenever possible. For more information about how prohibitions affect your design efficiency for CBC studies, please refer to the following sections:
Specifying prohibitions in CBC
The Prohibitions Grid
The prohibitions grid displays all the prohibitions currently in place for your project, one prohibition per row. You can specify prohibitions by:
•Directly typing integers within the grid (in ascending attribute order)
•Using the Add Prohibition button to specify a prohibition using a level selector via drop-down menus
•Importing prohibition specifications from a .csv file (using the Import button)
•Pasting values into the grid directly from Excel
For example, a "1" refers to either attribute 1 or level 1 when specified within the grid, etc. (Note: to specify that all levels of an attribute should be prohibited, specify level "0".)
The following buttons are available for helping you work with the Prohibitions Grid:
Add Prohibition
Lets you specify a prohibition using a level selector drop-down menu
Edit Prohibition
Opens the same dialog as the Add Prohibition button, but with the currently selected prohibition specified
Add Rows button
When clicked, adds 20 rows to the bottom of the grid
Add Columns
When clicked, adds 2 columns to the right of the grid
Cut
Cuts selected information to the Windows clipboard
Copy
Copies selected information to the Windows clipboard
Paste
Pastes selected information from the Windows clipboard into the grid
Import/Export
Imports or exports prohibitions to a comma-separated (.CSV) format
Within-Concept Prohibitions
Each prohibition is defined in terms of a set of attribute, level pairs. For example, the pair:
Attribute Level Attribute Level
1 2 2 4
indicates that attribute 1, level 2 should not appear together with attribute 2, level 4. That is a within-concept prohibition.
We could specify a 3-way prohibition, such as:
Attribute Level Attribute Level Attribute Level
1 2 2 4 3 2
indicating that the 3-way combination of attribute 1, level 2, attribute 2, level 4, and attribute 3, level 2 should never appear together within the same product concept. Up to n-way prohibitions may be defined, where n is the total number of attributes in your study.
Between-Concept Prohibitions
If the same attribute index appears two or more times within the same row, this indicates a between-concept prohibition. For example,
Attribute Level Attribute Level
1 2 1 4
indicates that attribute 1 level 2 should never be shown in competition with attribute 1 level 4 in a separate concept within the same conjoint task. Although we've shown just one attribute involved in the prohibition for simplicity, between-concept prohibitions can involve multiple attributes. Up to n-way prohibitions may be defined, where n is equal to the total number of attributes in your study. And, you can define prohibitions between concepts taken 3, 4, or more at a time (for as many concepts displayed within your conjoint or choice tasks). For example, the prohibition:
Attribute Level Attribute Level Attribute Level
1 2 1 4 1 5
indicates that attribute 1 levels 2, 4, and 5 should never appear together simultaneously within a conjoint task. Note that this doesn't prohibit attribute 1 levels 2 and 4 from appearing in competition with one another within the same conjoint task (as long as level 5 doesn't also appear as another concept within the same choice set).
Note: Attributes must appear in ascending order; when an attribute is repeated it marks the beginning of a new concept and must follow the same attribute sequence/pattern as the first concept.
Printing Prohibitions
If you click the Printer icon to print your list of prohibitions, the following notation applies.
Prohibitions are shown using (Attribute, Level) notation. Between-concept prohibitions show a '/' between concepts. For example:
1. (1, 2) (2, 3)
2. (2, 4) (3, 5) / (2, 1) (3, 6)