## E.5 Answers to Lecture 5 tutorial

### E.5.1 Answers to Sect. 5.1

1. 70% directly from the table.
2. $$281/(404 - 281) - 2.28$$.
3. For patients treated with ETI, about 278 die for every 100 that survive.
4. $$2.78/2.28 = 1.22$$.

### E.5.2 Answers to Sect. 5.2

1. $$45\div 240=18.75$$% of all college students in the sample have received one concussion, the same for all student types.
2. Not sure which is best; they do different things. I’d probably prefer (c).
3. Odds (non-athlete receiving 2+ concussions) is $$21\div(81-21) = 21\div 60 = 0.35$$. Non-athletes are 0.35 times as likely to receive two or more concussions than fewer than two. Or: For every 100 students with fewer than two concussions, there are 35 with two or more.
4. Odds (soccer player receiving 2+ concussions) is $$13\div(63-13) = 13\div 50 = 0.26$$. Soccer players are 0.26 times more likely to receive two or more concussions than fewer than two concussions.
5. OR: $$0.35 \div 0.26$$, or about $$1.35$$. The odds of a non-athlete receiving two or more concussions is about 1.35 times the odds of a soccer player receiving two or more concussions (that is, smaller odds for soccer players).
6. The better table is probably row percentages: The percentages of each type of students with given number of concussions.

### E.5.3 Answers to Sect. 5.3

1. Relative frequency.
2. Relative frequency.
3. Subjective.
4. Relative frequency.
5. Classical.