The quarterly sales levels (measured in millions of dollars) for Goodyear Tire are shown in Table P-13.

Question:

The quarterly sales levels (measured in millions of dollars) for Goodyear Tire are shown in Table P-13. Does there appear to be a significant seasonal effect in these sales levels? Analyze this time series to get the four seasonal indexes and determine the extent of the seasonal component in Goodyear's sales.
Table P-13

a. Would you use the trend component, the seasonal component, or both to forecast?
b. Forecast for third and fourth quarters of 1996.
c. Compare your forecasts to Value Line's.