What is a Subjective type criterion
Most of the facts in real life decision problems can be categorized as subjective type. When you are shopping for a house to buy, your objective can be
1. More trees around the house.
2. Spacious Garage
3. Close to a coffee shop etc
Notice that, there is no exact number that you care about. Rather, when you find a house, you may think that, hmm, it does not have much space in the garage. So, you may give it a rank of 3 out of 10. When you find a house with a big garage space that you like, you may rank it 9 out of 10. So, that is the idea of a Subjective type attribute. Even though garage size can be measured in square feet and you can measure the size, but you really do not care the exact size in square feet. Rather, you care if it looks big enough for you or too little.
The subjective type criterion is the most basic criterion data type. You should choose this data type when you want to express a utility value of a payoff directly using a slider as a percentage number.
The user interface for a Subjective type objective
After you have created a Subjective type objective, when you will set a payoff for a decision tree node, you will be presented with a slider to express your attribute. For example, say, you have a subjective type objective as "Minimize Cost". Then, in the Payoff window of a decision tree, you will see the following user interface for the subjective type criterion.
As the Objective is to Minimize the Cost, you see the smiley is in a sad expression for a high value. Let's change the slider value to a low value and you will see the face become happier.
Modeling a Subjective type objective
When you start the objective creation wizard, you will see the following screen. In order to model a Subjective type Objective, choose either "Maximize" or "Minimize" from the drop-down as shown below.
Say, you have entered the following criterion in the Objective start screen as shown below.
Then when you click the "Proceed" button, you will see the following question screen:
Click the button "Subjective type" from the above screen to make a criterion "Subjective type".
Editing the Objective
We have already explained how to invoke the objective editor. Once you create a subjective type objective and open the Objective editor for the Subjective type, you will see the following view.
How the utility value is inferred
The decision tree software will create a utility value for you based on the slider position as shown below. The following screenshot is taken from the payoff popup window of a decision tree node.
Notice that, when you have a goal to Minimize Distance, and when you place the slider position at 10%, the utility value is calculated as 100 - 10 = 90 Utils. As the goal is to Minimize the distance, the more is the distance (slider value), the less utility you get, right? That's why you will see a minus sign before the 10% value shown above. If the objective was to Maximize something, then the slider value would equal the utility value.