11.41 To project personnel needs for the Christmas shopping season, a department store wants to project sales for the season. The sales for the previous Christmas season are an indication of what to expect for the current season. However, the projection should also reflect the current economic environment by taking into consideration sales for a more recent period. The following model might be appropriate:

where

(All units are in thousands of dollars.) Data for ten previous years were used to fit the prediction equation, and the following values were calculated:

Use these results to determine whether there is evidence to indicate that the mean sales this Christmas are related to this year’s August sales in the proposed model.