7.1

31.

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

Interpretation 1. 15.87% of cell phone plans have monthly rates of $44 or less.

Interpretation 2. A randomly selected cell phone plan has a 15.87% probability of being $44 or less.

32.

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

Interpretation 1. 11.51% of refridgerators last 17 years or longer.

Interpretation 2. A randomly selected refridgerator has an 11.51% probability of lasting 17 years or longer.

33.

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

Interpretation 1. 2.28% of babies are have a birth weight of 4410 grams or more.

Interpretation 2.A randomly selected newborn has a 2.28% probability of having a birth weight of 4410 grams or more.

34.

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

Interpretation 1. 4.96% of 10-year-old males are 46.5 inches or taller.

Interpretation 2. A randomly selected 10-year-old-male has a 4.96% probability of being 46.5 inches or taller.

35.

Interpretation 1. 19.08% of human pregnancies last 280 days or longer.

Interpretation 2. A randomly selected pregnancy has a 19.08% probability of lasting 280 days or longer.

Interpretation 1. 34.16% of human pregnancies last between 230 and 260 (inclusive) days.

Interpretation 2. A randomly selected pregnancy has a 34.16% probability of lasting between 230 and 260 (inclusive) days.

36.

Interpretation 1. 33.09% of the time, Elena’s driving between refills at the gas station amounts to 26 miles per gallon or more.

Interpretation 2. A randomly selected period of Elena’s driving between refills at the gas station has a 33.09% probability of amounting to 26 miles per gallon or more.

Interpretation 1. 11.07% of the time, Elena’s driving between refills at the gas station amounts to 18 to 21 (inclusive) miles per gallon.

Interpretation 2. A randomly selected period of Elena’s driving between refills at the gas station has a 11.07% probability of amounting to 18 to 21 (inclusive) 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. 0.9998
  2. 0.7088
  3. 0.0129

11.

  1. 0.0228 + 0.0228 = 0.0456
  2. 0.0594 + 0.0052 = 0.0646
  3. 0.4051 + 0.1151 = 0.5202

13. -1.28

15. 0.67

17. 2.67, -2.67

33. (-1.34*7)+50 = 40.62

35. (0.88*7)+50 = 56.16

37.

shadenorm(mu = 21, sig = 1.0, below = -1000, col = "blue", dens=200)

  1. -0.1587 Approximately 16 of 100 randomly selected chicken eggs would hatch in less than 20 days. I.e. a randomly selected chicken egg has a 15.87% probability of hatching in less than 20 days.

  2. 0.1587 Approximately 16 of 100 randomly selected chicken eggs would hatch in more than 22 days. I.e. a randomly selected chicken egg has a 15.87% probability of hatching in more than 22 days.

  3. 0.4772 Approximately 48 of 100 randomly selected chicken eggs would hatch within 19 to 21 days. I.e. a randomly selected chicken egg has a 47.72% probability of hatching within 19 to 21 days.

  4. A randomly selected egg has a 0.13% probability of hatching in fewer than 18 days.

39.

  1. 0.8790 - 0.0136 = 0.8654
  2. 0.0132
  3. 0.7019
  4. 0.1210
  5. 0.9641 (96th percentile)
  6. 0.0359 (4th percentile)

41.

  1. 0.4013
  2. 0.1587
  3. 0.7631
  4. 0.7580
  5. 0.0951
  6. (0.0043) Yes. About 4 in 1000 have a gestation under 224 days.

43.

  1. 0.0764
  2. (0.0324) 3%
  3. 162 rods
  4. 11804 rods