7.1

31.

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

Interpretation 1. The probability that any random cell phone plan in the US is less than $44 is 0.1587.

Interpretation 2. 15.87% of US cell phone plans are under $44 per month.

32.

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

Interpretation 1. The probability that a refrigerator lasts more than 17 years is 0.1151..

Interpretation 2. 11.51% of refrigerators lasts longer than 17 years.

33.

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

Interpretation 1. The probability that a baby weighs more than 4410 grams is 0.0228.

Interpretation 2. 2.28% of full-term babies weigh more than 4410 grams.

34.

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

Interpretation 1. The probability that a 10-year-old males is shorter than 46.5 inches is 0.0496.

Interpretation 2. 4.96% of 10-year-old males are shorter than 46.5 inches.

35.

Interpretation 1. The probability that a human pregnancy is longer than 280 days is 0.1908.

Interpretation 2. 19.08% of human pregnancies last longer than 280 days.

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

Interpretation 2. 34.16% of human pregnancies take last between 230 days and 260 days.

36.

Interpretation 1. The probability that Elena exceeds 26 miles per gallon while fillin up her gas tank is 0.3309.

Interpretation 2. 33.09% of her gas tank fills exceed 26 miles per gallon.

Interpretation 1. The probability that Elena fills her gas tank between 18 and 21 miles per gallon is 0.1107.

Interpretation 2. 11.07% of her gas tank fills fall 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. za= -2.575; zb= 2.575.

33. In the 9th percentile, x= 40.62.

35. In the 81st percentile, x= 56.16.

37.

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

  1. The probability that a randomly selected fertilized chicken egg hatches in less than 20 days is 0.1587.
  2. The probability that a randomly selected fertilized chicken egg takes over 22 days to hatch is 0.1587.
  3. The probability that a randomly selected fertilized chicken egg hatches between 19 and 21 days is 0.4772.
  4. The probability that a randomly selected fertilized chicken hatches in less than 18 days is 0.0013.

39.

  1. The probability that a randomly selected 18-ounce bag of chips contains between 1000 and 1400 chocolate chips is 0.8658.

  2. The probability that a randomly selected 18-ounce bag of chips contains fewer than 1000 chocolate chips is 0.0132.
  3. 0.7019 of the bag of chips have more than 1200 chocolate chips.
  4. 0.1230 of the bag of chips have fewer than 1125 chocoloate chips.
  5. A bag of chips containing 1475 chocolate chips is at the 96th percentile.

  6. A bag of chips containing 1050 chocolate chips is at the 4th percentile.

41.

  1. 0.4013 of pregnancies last more than 270 days.
  2. 1.587 of pregnancies last fewer than 250 days.
  3. 0.7590 of pregnancies last between 240 and 280 days.
  4. The probability that a pregnancy lasts more than 280 days is 0.1894.
  5. The probability that a pregnancy lasts no more than 245 days is 0.0951.
  6. Yes, only 4 in 1000 births are premature.

43.

  1. 0.0764 of the rods are less than 24.9 cm.
  2. 0.0324 of the rods will be discarded.
  3. If 5000 rods are manufactured in a day,the plant manager should expect to discard 162 rods.
  4. For an order of 1000 rods, the plant manager should manufacture 11,804 rods.

45.

  1. Yes.
  2. The probability that the favored team wins by 5 or mroe points relative to the spread is 0.3228.
  3. The probability that the favored team loses by 2 or more points relative to the spread is 0.4286.

47.

  1. The 17th percentile for incubation time is 20 days.
  2. The incubation times that make up the middle 95th of fertilzied chicken eggs are between 19 and 23 days.

56.