7.1

31.

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

Interpretation 1. 15.87% of cell phone plans in the U.S. are less than $44/per month.

Interpretation 2. The probability that a randomly selected cell plan in the U.S. is less than $44 per month is .1587.

32.

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

Interpretation 1. 11.51% of refrigerators lasted over 17 years.

Interpretation 2. The probability is .1151 that a randomly selected refrigerator lasts more than 17 years

33.

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

Interpretation 1. 2.28% of all full-term babies have a birth weight of more than 4410 grams.

Interpretation 2.The probability is .0228 that the birth weight of a randomly selected full-term baby is more than 4410 grams.

34.

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

Interpretation 1. The height of 4.96% of all 10-year-old men is less than 46.5 inches tall.

Interpretation 2. The probability is .0496 that the height of a randomly selected 10-year-old male is less than 46.5 inches.

35.

Interpretation 1. The proportion of human pregnancies that last more than 280 days is .1908.

Interpretation 2. The probability that a randomly selected human pregnancy lasts more than 280 days is .1908.

Interpretation 1.The proportion of human pregnancies that last between 230 and 260 days is .3416.

Interpretation 2. The probability that a randomly selected pregnancy lasts between 230 and 260 days is .3416.

36.

Interpretation 1. The proportion of miles per galon that is between 21.5MPG and 26 MPG is .3309.

Interpretation 2. The probability Elena uses more than 26 MPG is .3309.

Interpretation 1. The proportion of gas milage that lasts between 18 and 21 MPG is .1107.

Interpretation 2. The probability that the model for the car’s gas milage lasts more than 21 MPG is .1107 .

7.2

5.

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

7.

  1. .9987. (b).9441.
  2. .0375.
  3. .0009.

9.

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

11.

  1. .0456.
  2. .9646.
  3. .5203.

13. -1.28.

15. .67.

17. z1= -2.575; z2= 2.575

33. x = 40.62 is at the 9th percentile.

35. x = 56.16 is at the 81st percentile .

37.

  1. p(x<20)= .1587.
  2. p(x>22) = .1587.
  3. p(10 /= 5) = .3228 .
  4. p (x</= -2) = .4286.
  5. The favored team is equally likely to win or lose relative to the spread. A mean of 0 indicates the spreads are accurate.

47.

  1. The 17th percentile for inincubation time is 20 days
  2. From 10 to 23 days make up in the middle of 95% of incubation times of the eggs.

56. The probability as .9999 means the event is highly likely, while reporting the probability as 1.00 might give off the impression that the event is certain.