In the article “Age as a prognostic factor for complications of major head and neck surgery” published in the Archives of Otolaryngology – Head & Neck Surgery (Boruk et al., 2005), the authors reported the results given in Table 9.33 for a regression model to predict the hospital length of stay that included a dummy variable for the sex of an individual (Sex) and a dummy variable indicating whether or not an individual was younger than 70 or older (Age). Use the information in Table 9.33 to answer the following:

(a) Does the sex of an individual appear to be an important variable for predicting the hospital length of stay? Explain.

(b) Does it appear that knowing whether or not an individual is younger than 70 is useful in predicting the hospital length of stay? Explain.

(c) Can the simultaneous importance of the dummy variables Sex and Age be tested?

Explain.

(d) Based on the information in Table 9.33 which variables appear to be important for predicting the hospital length of stay?