## D.14 Answers: Numerical summaries for qualitative data

Answers to exercises in Sect. 14.9.

Answer to Exercise 14.1: 1. Vomited: 0.50 had beer then wine; 0.50 had wine only.
Didn’t vomit: 0.738 had beer then wine, 0.262 had wine only. They tell us the proportion that drank various things, among those who did and didn’t vomit. 2. Beer then wine: 8.8% vomited and 91.2% didn’t; Wine only: 21.4% vomited and 78.6% didn’t. They tell us the percentage that vomited, for each drinking type. 3. $$(6 + 6)/(6 + 6 + 62 + 22) = 0.125$$. 4. $$6/22 = 0.2727$$. 5. $$6/62 = 0.096774$$. 6. $$0.27272/0.096774 = 2.82$$. 7. $$0.096774/0.27272 = 0.354$$.
Answer to Exercise 14.2: 1. $$91/(91 + 188) = 0.32616$$. 2. $$188/91 = 2.0659$$, or about 2.07. 3. $$22/13 = 1.6923$$, or about 1.69. 4. $$13/(13 + 22) = 0.37142$$, or about 37.1%. 5. $$2.0659/1.6923 = 1.22$$.
Answer to Exercise 14.3: 1. 21/114, or about 18.4%. 2. 14/54, or about 25.9%. 3. 7/60, or about 11.7%. 4. 21/93, or about 0.226. 5. 14/40, or 0.35. 6. 7/53, or about 0.132. 7. 0.35/0.132, or about 2.7. 8. The odds of no August rainfall in Emerald is 2.7 times higher in months with non-positive SOI.
Answer to Exercise 14.4: 1. 45.9%. 2. 61.4%. 3. 0.848. 4. 1.59. 5. 1.15. 6. 0.533. 7. The odds of reporting back pain from carrying school bags, comparing boys to girls.