In a study by Alicikus et al. (A-7), long-term control of prostate cancer receiving radiotherapy was examined in patients after 10 years. The authors using Cox regression analysis to analyze these data, which resulted in the data summarized in the table below. For these data:

(a) Calculate the parameter estimates for the Cox regression model.

(b) Provide an explanation of the hazard ratios (HR) and their meaning.

(c) For age, provide an alternative measure for the HR and provide its meaning in terms of the percent change in years.

Variable Hazard Ratio (HR) 95% CI for HR p-value Age 1.02 (.96, 1.08) .51 Hormone therapy (yes vs. no) .89 (.44, 1.81) .75 Pre-PSA, >10 ng/mL vs. 10 ng/mL 2.41 (1.19, 4.88) .015 Tumor classification 1.42 (1.17, 1.71) <.001