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.
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.