How to Use Decision.Help to Make a Decision

Step 1: List Your Decision Alternatives

To use Decision.Help, start by listing the alternatives you are considering.

For example, if you are choosing the best car to buy, the alternatives would be the different makes and models of cars you are considering.

Step 2: List Your Criteria

Next, list the criteria that will influence your decision. These are the factors that matter to you when comparing alternatives. For a car purchase, common criteria include:

• Price (lower is usually better)
• Miles per gallon (MPG) / Fuel efficiency (higher is better)
• Running costs (maintenance, insurance, and tax)
• Reliability (how often the car breaks down)
• Safety rating (crash test results and safety features)
• Performance (acceleration, top speed, handling)
• Comfort and interior features (seat quality, technology, space)
• Cargo space (important if you carry luggage, equipment, or a stroller)
• Environmental impact (electric, hybrid, emissions)
• Brand reputation (customer reviews, resale value)

Step 3: Define Objective and Subjective Criteria

Some criteria are objective and can be measured with numbers, like price or miles per gallon. For these, you decide whether a higher or lower number is better. For example:

• Miles per gallon – higher is better.
• Price – lower is better.

Other criteria are subjective and based on personal preference. For instance, if you want a car that looks sporty, you would need to rate how sporty each option appears to you.

You will be asked if you can give your criteria a number or not. If not, then it's a subjective criteria.

Step 4: Assign Weights to Each Criterion

After listing your criteria, assign a weight to each one based on its importance to you. This is a number from 1 to 100. The greater the number, the more important it is to you.

• If you are on a tight budget, price might be your highest priority.
• If you only drive short distances, fuel efficiency might not be a major concern.

Step 5: Enter Values for Each alternative

Finally, enter the actual values for each alternative under each criterion. For example, for each car you are considering, enter its price, fuel efficiency, reliability rating, and so on.

Some criteria may have a range of values, especially if there is some uncertainty involved in their estimation. For example, in the case of buying a car, the actual miles per gallon (MPG) or energy consumption (kWh per mile for EVs) depends on driving conditions (urban vs. motorway driving), weather, and driving style. So it could be 25-35 MPG.

Step 6: Calculate the Best alternative

Once all the information is entered, Decision.Help will calculate the best alternative for you based on your priorities.

The results will be displayed in a graph where the best alternatives for you will be to the right. The width and height of an alternative's curve illustrates the uncertainty present, with wider and shorter distributions having greater uncertainty. Whereas a tall and narrow curve is more certain. So, if two curves have a similar score, you should pick the alternative whose curve is taller and narrower unless you are comfortable with uncertainty.

You can create further 'what if' scenarios by varying the criteria weights and alternative values and recalculating the results. For example, what would be the best alternative if you increase the weight of one of the criteria?