Consider the following set of sales data, given in millions of dollars:
a. Plot these data. Based on your visual observations, what time-series components are present in the data?
b. Determine the seasonal index for each quarter.
c. Fit a linear trend model to the data and determine the MAD and MSE values. Comment on the adequacy of the linear trend model based on these measures of forecast error.
d. Provide a seasonally unadjusted forecast using the linear trend model for each quarter of the year 2010.
e. Use the seasonal index values computed in part b to provide seasonal adjusted forecasts for each quarter of 2010. |

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