The intent of a study by Weaver et al. (A-4) was to assess whether occult lymph node metastases are important indicators of disease recurrence or survival in breast cancer patients. The data below provide some of the pertinent results of a Cox regression model for these data.

(a) Calculate the regression parameter coefficients for each variable.

(b) Provide an interpretation of these results using the concepts learned in this section.

Variable Hazard Ratio (HR) 95% CI for HR p-value Age (50þ vs. <50) 1.69 (1.24, 2.31) .001 Tumor size (>2 cm vs.  2 cm) 1.32 (.98, 1.76) .060 Chemotherapy vs. no chemotherapy .88 (.68, 1.13) .31 Radiation vs. no radiation 0.54 (.40, .73) .001