An estimated odds ratio for adult females between the presence of squamous cell carcinoma (yes, no) and smoking behavior (smoker, nonsmoker) equals 11.7 when the smoker category has subjects whose smoking level s is 0 < s < 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 < s < 20) equals 2.2.