7.1

31.

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

  1. 15.87% of the cell phone plans in the US is less than $44 per month

The probability is 0.1587 that a randomly selected cell phone plan in US is less than $44 per month

32.

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

  1. 11.51% of the lives of refrigerators is greater than 17 years.

  2. The probability is 0.1151 that a randomly selected life of a refrigerator in the US is greater than 17 years.

33.

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

  1. 2.28% of the birth weights of full-term babies is greater than 4410 grams.

  2. The probability is 0.0228 that a randomly selected birth weight of full term babies is greater than 4410 grams.

34.

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

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

Interpretation 2. The probability that a randomly selected 10 year old male to be less than 46.5 inches 0.0496.

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 pregnanacy lasts between 230 and 260 days is 0.3416,

36.

Interpretation 1. The porportion of the miles per gallon for each fill-up being greater than 26 is 0.3309

Interpretation 2. The probability that a randomly selected miles per gallon of a fill up being greater than 26 is .33009

Interpretation 1. The proportion of the miles per gallon for each fill that falls between 18 and 21 is 0.1107

Interpretation 2. The probability that a randomly selected mils per gallon for each fill that fallls between 18 and 21 is 0.1106

7.2

5.

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

7.

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

9.

  1. Area = 0.9586
  2. Area = 0.2088
  3. Area = 0.8479

11.

  1. Area = 0.0456
  2. Area = 0.0646
  3. Area = 0.5203

13. z = -1.28

15. z = 0.67

17. z1 = -2.575 ; z2 =2.575

33. x = 40.62 is at 9th percentile

35. x = 56.16 is at 81st percentile

37.

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

  1. P (X<20) = 0.1587. If 100 eggs are randomly selected, we would expect 16 to incubate in less than 20 days.
  2. P(x > 22) = 0.1587. If 100 eggs are randomly selected, we would expect 16 to incubate in more than 22 days.
  3. P(19≤x≤21) = 0.4772. If 100 eggs are randomly selected
  4. yes; P(x<18) = 0.0013. Model suggests 1 egg in 1000 incubates in less than 18 days

39.

  1. P (1000 ≤ x ≤1400) = 0.8658
  2. P ( X < 1000) = 0.0132
  3. 0.709 of the bags have more than 1200 chocolate chips
  4. 0.1230 of the bags have more than 1200 chocolate chips
  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 of pregnancies last more than 270 days
  2. 0.1587 of preganancies last fewer than 250 days
  3. 0.7590 of pregnancies last between 240 and 280 days
  4. P (x > 280) = 0.1894
  5. P (X ≤ 245) = 0.0951
  6. Yes ; 0.0043 of births are very preterm. So about 4 births in 1000 biths are very preterm.

43.

  1. 0.0764 of the rods have a length of less than 24.9 cm.
  2. 0.0324 of the rods will be discarded.
  3. THe plant manager expeccts to discard 162 of the 5000 rods manufactured.
  4. To meet the order, the plant manager should manufacture 11,804 rods