Historical data is available on which to base the forecast. Forecasts for groups of items tend to be more accurate than forecasts for individual items. The sales staff is least affected by changing customer needs. The sales force can easily distinguish between customer desires and probable actions. The sales staff is often aware of customers' future plans.
Salespeople are least likely to be influenced by recent events.
Simple exponential smoothing is being used to forecast demand. The previous forecast of 66 turned out to be four units less than actual demand. Deviations around the line are normally distributed. Predictions are to be made only within the range of observed values of the predictor variable.