7.1

31.

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

Interpretation 1.15.87% of the cell phones plans in United States are less than 44$ per month.

Interpretation 2.The probability is 0.1587 that a randomly chosen cell phone plans will less than 44$ per month.

32.

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

Interpretation 1. 11.51% of refrigerators’ lives are more than 17 years.

Interpretation 2.The probability is 0.1151 that a randomly chosen refrigerator life will be more than 17 years.

33.

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

Interpretation 1. 2.28% of birth weights of full-term babies are more than 4410 grams.

Interpretation 2.The probability is 0.0228 that a randomly chosen baby’s weight will be more than 4410 grams.

34.

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

Interpretation 1. 4.96% of heights of 10-year-old males are less than 46.5 inches.

Interpretation 2. The probability is 0.0496 that a randomly chosen 10-year-old male’s height will less than 46.5 inches.

35.

Interpretation 1.19.08% of human pregnancy are more than 280 days.

Interpretation 2.The probability is 0.1908 that a randomly chosen human pregnancyday will be 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 that a randomly chosen human pregnancy lasts between 230 and 260 days is 0.3416.

36.

Interpretation 1. 33.09% of a toyota car runs more than 26 miles per gallon.

Interpretation 2.The probability is 0.3309 that a randomly chosen toyota car runs more than 26 miles per gallon.

Interpretation 1.The proportion of the toyota car runs between 18 to 21 miles per gallon is 0.1107.

Interpretation 2. The probability that a randomly chosen toyota car runs between 18 to 21 miles per gallon is 0.1107.

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

35. x=56.16

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 amlost 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, we would exepct almost around 48 to incubate in between 19 and 21 days. (e)yes it will be usual. P(x<18)=0.0013. Becasue the model shows that 1 egg in 1000 incubates in less than 18 days.

39.

  1. p(1000???x???1400)=0.8658 (b)p(x<1000)=0.0132
  2. 0.7019of the bags have more than 1200 chocolate chips. (d)0.1230 of the bags have fewer than 1125 chocolate chips.
  3. A bag that contains 1475 chocolate chips is at the 96th percentile.
  4. 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 pregnancies last less 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. ao about 4 births in 1000 births are very preterm.

43.

  1. 7.64% of the roads have a length if less than 24.9cm.
  2. 3.24% of the roads will be discarded
  3. The plant manager expects to discard 162 of 5000 roads manufactured.
  4. To meet the order, the plant manager should manufacture 11804.

45. (a) The favored team is qually possibly to win or to lose relative to the spread. Yes, a mean which is 0 implies the spreads are accurate. (b) p(x???5)= 0.3228 (c) p(x???-2)= 0.4286

47.

  1. The 17th persontile for incubation time is 20 days.
  2. From 19 to 23 days make up the middle 95% of incubation times of the eggs.

56. SAT scores scored higher. Because we can count the Z scores of both ACT and SAT exams. ACT gets 0.961 and SAT gets 1.019. 1.019>0.961 so it scores higher on SAT exam.