Using Judgmental Forecasts

Judgmental forecasts are based on subjective views – often the options of experts in the field. Suppose a company is about to market an entirely a new product, or the board is looking at plans for 25 years in the future. They won’t have any relevant historical data for a quantative forecast. Sometimes there is a complete absence of data, and at other times the data is unreliable or irrelevant to the future.

 Quantative forecasts are always more reliable, but when you don’t have the necessary data, you have to use a judgmental method. There are five widely used methods:

• Personal insight. This uses a single person who is familiar with the situation to produce a forecast based on his or her own judgment. This is the most widely used forecasting method – but is unreliable and often gives very bad results.
• Panel consensus. This collects together a group of experts to make a forecast. If there is no secrecy and the panel talk freely and openly, you can find a genuine consensus. On the other hand, there may be difficulties in combining the views of different people.
• Market surveys. Sometimes even groups of experts don’t have enough knowledge to give a reasonable forecast about, for example, the launch of a new product. Then market surveys collect data from a sample of potential customers, analyze their views and make inferences about the population at large.
• Historical analogy. If you are introducing a new product, you might have a similar product that you launched recently, and assume that demand for the new product will follow the same pattern. If a publisher is selling a new book, it can forecast the likely demand from the actual demand for a similar book it published earlier.
• Delphi method. For this you contact a number of experts by post and give each a questionnaire to complete. Then you analyze the replies from the questionnaires and send summaries back to the experts. You ask them if they would like to reconsider their original replay in the light of summarized replies from others. This is repeated several times – usually between three and six – until the range of options is narrow enough to help with decisions.

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