Introduction to Probability and Statistics for Engineers and Scientists

Problems 429

40.Redo Problem 5 under the assumption that the variance of the gain in reading

speed is proportional to the number of weeks in the program.

41.The following data relate the proportions of coal miners who exhibit symptoms of

pneumoconiosis to the number of years of working in coal mines.

Years Working Proportion Having Penumoconiosis

50

10 .0090

15 .0185

20 .0672

25 .1542

30 .1720

35 .1840

40 .2105

45 .3570

50 .4545

Estimate the probability that a coal miner who has worked for 42 years will have

pneumoconiosis.

42.The following data set refers to Example 9.8c.

Number of Cars Number of Accidents

(Daily) (Monthly)

2,000 15

2,300 27

2,500 20

2,600 21

2,800 31

3,000 16

3,100 22

3,400 23

3,700 40

3,800 39

4,000 27

4,600 43

4,800 53

(a) Estimate the number of accidents in a month when the number of cars using

the highway is 3,500.