11.36 In hopes of increasing the company’s share of the fine-food market, researchers for a meat-processing firm that prepares meats for exclusive restaurants are working to improve the quality of its hickory-smoked hams. One of their studies concerns the effect of time spent in the smokehouse on the flavor of the ham. Hams that were in the smokehouse for varying amount of time were each subjected to a taste test by a panel of ten food experts. The following model was thought by the researchers to be appropriate:

Y = b0 + b1t + b2t 2 + e where Y  mean of the taste scores for the ten experts t  time in the smokehouse (hours)
Assume that the least-squares model estimated using a sample of 20 hams is yN = 20.3 + 5.2t - 0.0025t 2 and that  0.0011. The coefficient of determination is R2  0.79.
a Is there evidence to indicate that the overall model is useful? Test at  0.05.
b Is there evidence to indicate that the quadratic terms is important in this model? Test at  0.05.