7.1

31.

shadenorm(mu = 62, sig = 18, below = 44, col = "blue", dens = 200)

Interpretation 1. 15.87% of the cell phone plans in the United States are less than $44 per month.

Interpretation 2. The probability is 0.1587 that a randomly selected cell phone plan in the United States is less than $44 per month.

32.

shadenorm(mu = 14, sig = 2.5, above = 17, col = "blue", dens = 200)

Interpretation 1. 11.51% of the refrigerators last for more than 17 years.

Interpretation 2. The probability is 0.1151 that a randomly selected refrigerators last more than 17 years.

33.

shadenorm(mu = 3400, sig = 505, above = 4410, col = "blue", dens=200)

Interpretation 1. 2.28% of all full-term babies have a birth weight of more than 4410 grams.

Interpretation 2. The probability is 0.0228 that the birth weight of a randomly chosen full-term baby is more than 4410 grams.

34.

shadenorm(mu = 55.9, sig = 5.7, below = 46.5, col = "blue", dens=200)

Interpretation 1. 4.96% of 10-year-old males have a height less than 46.5 inches.

Interpretation 2. The probability is 0.0496 that the height of a randomly chosen 10-year-old males is less than 46.5 inches.

35.

Interpretation 1. The proportion of human pregnancies that last more than 280 days is 0.1908.

Interpretation 2. The probability that a randomly selected human pregnancy lasts more than 280 days is 0.1908.

Interpretation 1. The proportion of human pregnancies that last between 230 and 260 days is 0.3416.

Interpretation 2. The probability that a randomly selected human pregnancy lasts between 230 and 260 days is 0.3416.

36.

Interpretation 1. The proportion of gas mileage that more than 26 miles per gallon is 0.3309.

Interpretation 2. The proability that a randomly selected gas mileage that more than 26 miles per gallon is 0.3309.

Interpretation 1. The proportion of gas mileage that last between 18 and 21 miles per gallson is 0.1107.

Interpretation 2. Theprobability that a randomly selected gas mileage last between 18 and 21 miles per gallon is 0.1107.

7.2

5.

  1. 0.0071
  2. 0.3336
  3. 0.9115
  4. 0.9998

7.

  1. 0.9987
  2. 0.9441
  3. 0.0375
  4. 0.0009

9.

  1. 0.9586
  2. 0.2088
  3. 0.8479

11.

  1. 0.0456
  2. 0.0646
  3. 0.5203

13. -1.28

15. 0.67

17. z1=-0.257 z2=0.257

33. 40.62

35. 56.16

37.

  1. 0.1587
  2. 0.1587
  3. 0.4772
  4. It would be unusual, because P(X<18)=0.0013, thus about 1 egg in 1000 hatches in less than 18 days.

39.

  1. 0.8658
  2. 0.0132
  3. 0.7019
  4. 0.1230
  5. A bag that contains 1475 chocolate chips is at the 96th percentile.
  6. A bag that contains 1050 chocolate chips is at the 4th percentile.

41.

  1. 0.4013
  2. 0.1587
  3. 0.7590
  4. 0.1894
  5. 0.0951
  6. Yes, 0.0043 of births are very preterm. Thus about 4 births in 1000 births are very preterm.

43.

  1. 0.0764
  2. 0.0324
  3. 162
  4. 11,804

45.

  1. 0.3228
  2. 0.4286
  3. The favored team is equally likely to win or lose relative to the spread. Yes, a mean of 0 implies the spreads are accurate.

47.

  1. 20 days.
  2. 19 to 23 days.

56. The proportion of an ACT score that is less than 26 is 0.8315. The proportion of a SAT score that is less than 1240 is 0.8461. Since 0.8461>0.8315. The SAT score is relatively better because it scores better than more proportion of randomly selected scores.