# Stats 100 Chapter 17, 18, 19 Textbook Exercise Answers.docx

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6 May 2012

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Stats 100 Answers

Chapter 17 (3, 7, 9, 17, 21, 25)

3) long trials of this experiment suggest about 40% heads

7) results will vary with the type of thumbtack used

9) 0 b) 1 c) 0.01 d) 0.6

17) If two people talk at length, they will eventually discover something in common

21) The law of averages is no more reliable for forecasting the weather (in the short run) than it is for

other predictions

25) 51, 507, 5031, 50074; 1, 7, 31, 74 heads away from half the number of tosses

Chapter 18 (7, 13, 15, 19)

7) In Models 1, 3, and 4 the probabilities do not sum to 1; Model 4 has probabilities greater than 1. Model

2 is legitmate

13a) 0.24

b) 0.23

c) 0.47; 0.5

15a) 0.518 to 0.582 b) 0.16

19) about 50%. Probability is the proportion of times the outcome would occur in a very long series of

repetitions

b) about 68%

c) answers will vary

Chapter 20 (5, 9, 15, 17)

5) $0.4996

9) 8700 units

15) $99.625

b) although the probability is very small, having to pay $100,000 would probably be financially disastrous

for you

c) the insurance company will earn about $100 per policy by the law of large numbers, and because they

sell lots of policies , they can afford the rare cause of paying $100,000

17a) 2.24

b) assign 0 and 1 to an A, 2 to 4 a B, 5 to 7 a C, 8 a D, and 9 an F. Results will vary with the starting line

in Table A