7.1

31.

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

Interpretation 1. The probability that a randomly selected cell phone plan costs less than $44 is 0.1587.

Interpretation 2. The proportion of cell phone plans that cost less than $44 is 0.1587.

32.

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

Interpretation 1. The probability that the life of a randomly selected refrigerator is over 17 years is 0.1151.

Interpretation 2. The proportion of the life of refrigerators are over 17 years is 0.1151.

33.

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

Interpretation 1. The probability that the birth rate of a randomly selected full-term baby is more than 4410 grams is 0.0228.

Interpretation 2.The proportion of the birth rate of full-term babies are more than 4410 grams is 0.0228.

34.

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

Interpretation 1. The probability that a randomly selected 10-year-old male is below 46.5 inches is 0.0496.

Interpretation 2. The proportion of 10-year-old males are below 46.5 inches is 0.0496.

35.

Interpretation 1. The probability that a randomly selected human pregnancy lasts over 280 days is 0.1908.

Interpretation 2. The proportion of human pregnancies that are more than 280 days is 0.1908.

Interpretation 1. The probability that a randomly selected human pregnancy is between 230 and 260 days is 0.3416.

Interpretation 2. The proportion of human pregnancies that are between 230 and 260 days is 0.3416.

36.

Interpretation 1. The probability that a randomly selected time that Elena filled up her gas tank is more than 26 miles per gallon is 0.3309.

Interpretation 2. The proportion of gas tank fill ups that are more than 26 miles per gallon is 0.3309.

Interpretation 1. The probability that a randomly selected time that Elena filled up her gas tank is between 18 and 21 miles per gallon is 0.1107.

Interpretation 2. The proportion of gas tank fill ups that are between 18 and 21 miles per gallon is 0.1107.

7.2

5.

  1. .0071
  2. .3336
  3. .9115
  4. .9998

7.

  1. .9987
  2. .9441
  3. .0375
  4. .0009

9.

  1. .9586
  2. .2088
  3. .8479

11.

  1. .0228
  2. .0594
  3. .4052

13. -1.28

15. -0.67

17. -2.57 and 2.57

33. 40.62

35. 56.16

37.

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

  1. The probability that the randomly selected egg hatches in less than 20 days is .1587. The proportion of eggs that hatch in less than 20 days is .1587.
  2. The probability that the randomly selected egg hatches in over than 22 days is .1587. The proportion of eggs that hatch in over than 22 days is .1587.
  3. The probability that the randomly selected egg hatches between 19 and 21 days is .4772. The proportion of eggs that hatch between 19 and 21 days is .4772.
  4. It would be unusual for an egg to hatch in less than 18 days because the probability of this happening is only .0013.

39.

  1. The The probability that a randomly selected 18-ounce bag of Chips Ahoy! has between 1000 and 1400 chocolate chips is 0.7632.
  2. The The probability that a randomly selected 18-ounce bag of Chips Ahoy! contains fewer than 1000 chocolate chips is 0.0132.
  3. The The probability that a randomly selected 18-ounce bag of Chips Ahoy! contains more than 1200 chocolate chips is 0.7019.
  4. The probability that a randomly selected 18-ounce bag of Chips Ahoy! contains fewer than 1125 chocolate chips is 0.1230.
  5. 96th percentile
  6. 4th percentile

41.

  1. The proportion of human pregnancies that last more than 270 days are 0.4013.
  2. The proportion of human pregnancies that last less than 250 days are 0.1587.
  3. The proportion of human pregnancies that last between 240 and 280 days are 0.0759.
  4. The probability that a randomly selected human pregnancy will that last more than 280 days are 0.1894.
  5. The probability that a randomly selected human pregnancy will that last no more than 245 days are 0.0951.
  6. A very preterm baby is very unusual because the probability that a baby’s gestation period is less than 224 days is 0.0043.

43.

  1. The proportion of rods that have a length less than 24.9cm is 0.0764.
  2. The proportion of rods that will be discarded is 0.9676.
  3. If 5000 rods are manufactured, 4838 rods are expected to be discarded.
  4. 11,804 rods should be manufactured in order to get 10,000 rods between 24.9cm and 25.1cm.