5.25 Table 5.14 is from a study of nonmetastatic osteosarcoma described in the LogXact 7 manual (Cytel Software, 2005, p. 171). The response is whether the subject achieved a three-year disease-free interval. Table 5.14. Data for Problem 5.25 Disease-Free Lymphocytic Osteoblastic Infiltration Sex Pathology Yes No High Female No 3 0 High Female Yes 2 High Male No 4 00 High Male Yes 1 0 Low Female No 5 0 Low Female Yes 3 2 Low Male No 5 4 Low Male Yes 6 11 a. Show that each predictor has a significant effect when it is used individually without the other predictors. b. Try to fit a main-effects logistic regression model containing all three predic- tors. Explain why the ML estimate for the effect of lymphocytic infiltration is infinite. c. Using conditional logistic regression, conduct an exact test of the hypothesis of no effect of lymphocytic infiltration, controlling for the other variables. Interpret. d. Using conditional logistic regression, find a 95% confidence interval for the effect in (c). Interpret.