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 all refrigerators are kept for more than 17 years.

Interpretation 2. The probability is 0.1151 that a randomly selected refrigerator is more than 17 years old.

33.

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

Interpretation 1. 2.28% of all full-term babies has a birth weight of at least 4410 grams.

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

34.

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

Interpretation 1. The proportion of 10- year-old males who are less than 46.5 inches tall is 0.0496.

Interpretation 2. The probability is 0.0496 that a randomly selected 10-year-old male is less than 46.5 inches tall.

35.

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

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

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

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

36.

Interpretation 1. The proportion of times that Elena gets more than 26 miles per gallon is 0.3309.

Interpretation 2. The probability is 0.3309 that a randomly selected fill-up yields at least 26 miles per gallon is 0.3309.

Interpretation 1. The proportion of times that Elena gets between 18 and 21 miles per gallon is 0.1107.

Interpretation 2. The probability is 0.1107 that a randomly selected fill-up yields between 18 and 21 miles per gallon.

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. z=-1.28

15. z=0.67

17. -2.575 and 2.575

33. 50+(−1.34)(7)=40.62

35. 50+0.88(7)=56.16

37.

  1. 0.1587
  2. 0.1587
  3. 0.4772
  4. 0.0013

39.

  1. 0.8658
  2. 0.0132
  3. 70.19%
  4. 12.30%
  5. 96th percentile
  6. 4th percentile

41.

  1. 40.13%
  2. 15.87%
  3. 75.90%
  4. 0.1894
  5. 0.0951
  6. 0.0043

43.

  1. 7.64%
  2. 3.24%
  3. 162
  4. 11804 rods

45.

  1. 0.3228
  2. 0.4286
  3. Yes, the spreads are accurate for games in which a team is favored by 12 or fewer points. The favored team is equally to win or lose relative to the spread if mean is 0.

47.

  1. 20 days
  2. between 19 and 23 days

56. for ACT: z=0.96 P=0.8351 for SAT: z=1.02 p=0.8461 So, did better on SAT