## A.5 Answers to Lecture 5 tutorial

### A.5.1 Answers to Sect. 5.7

1. See Table A.1. 2. $$60/320 = 0.1875$$. A worker with SMND is 0.1875 times as likely to have worked with metal than not. 3. $$33/344 = 0.096$$. A worker with SMND is 0.096 times as likely to have worked with metal than not. 4. $$0.1875/0.096 = 1.95$$; the odds are about twice as great. 5. $$60 \div 380 = 15.8$$%. 6. $$33\div 377 = 8.8$$%. 7. Probably not: big difference seen in a large size sample.
TABLE A.1: SMND cases, and whether they had worked with metals
Worked with metals Did not work with metals Total
SMND cases 60 320 380
Controls 33 344 377
Total 93 664 757

### A.5.2 Answers to Sect. 5.8

1. Observational. 2. The percentage of residents in each area that detected the smell at the given frequency. So, for example, the first number in the first column would become $$48\div 97\times 100 = 49.5$$. This means that $$49.5$$% of the sample that lived in Area I detected the odour at least once a week. 3. For example, the percentage of residents who detected an odour at least once a week, who lived in Area I. 4. Probably column percentages. 5. $$77\div291 = 26.46\%$$.