An estimated odds ratio for adult females between the presence of squamous cell carcinoma (yes, no) and smoking behavior (smoker, non-smoker) equals 11.7 when the smoker category consists of subjects whose smoking levels is 0 < < 20 cigarettes per day; it is 26.1 for smokers with s 20 cigarettes per day (R. C. Brownson et al., Epidemiology, 3: 61-64, 1992). Show that the estimated odds ratio between carcinoma (yes, no) and the smoking levels (s 20, 0