7.1

31.

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

Interpretation 1. The probability that a randomly selected cell phone is less than $44 is .1587.

Interpretation 2. 15.87% of the cell phone plans are less than $44.

32.

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

Interpretation 1. The probability that a randomly selected refrigerator is older than 17 years is .1151.

Interpretation 2. 11.51% of refrigerators are greater then 17 years old.

33.

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

Interpretation 1. The probability that a randomly selected baby at full term has a birth weight of atleast 4410grams is .0228.

Interpretation 2. 2.28% of full term babies have a birth weight of atleast 4410grams.

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 has a height less than 46.5inches is .0496.

Interpretation 2. 4.96% of 10 year old males have a height less than 46.5inches.

35.

Interpretation 1. The percentage of pregnancies that are greater than 280 days is 19.08%.

Interpretation 2. The probability that a pregnancy is greater than 280 days is .1908.

Interpretation 1. The percentage of pregnancies lasting between 230 and 260 days is 34.16%.

Interpretation 2. The probabiliy of having a pregnancy last between 230 and 260 days is .3416.

36.

Interpretation 1. The probability that the miles per gallon on a car is greater than 26 is .3309.

Interpretation 2. 33.09% of cars have a miles per gallon that is greater then 26.

Interpretation 1. The probability that the miles per gallon on a car is less than 21 is .1107.

Interpretation 2. 11.07% of cars have a miles per gallon that is less than 21.

7.2

5.

  1. The area to the left of -2.45 is .0071.
  2. The area to the left of -0.43 is .3336.
  3. The area to the left of 1.35 is .9915.
  4. The area to the left of 3.49 is .9998.

7.

  1. The area to the right of -3.01 is .9987.
  2. The area to the right of -1.59 is .9441.
  3. The area to the right of 1.78 is .0375.
  4. The area to the right of 3.11 is .0009.

9.

  1. The area that lies between -2.04 and 2.04 is .9586.
  2. The area that lies between -0.55 and 0 is .2088.
  3. The area that lies between -1.04 and 2.76 is .8479.

11.

  1. The area under the curve to the left of -2 and to the right of 2 is .0456.
  2. The area under the curve to the left of -1.56 and to the right of 2.56 is .0649.
  3. The area under the curve to the left of -0.24 and to the right of 1.20 is .5203.

13. z = -1.28

15. z = .68

17. The zscores that seperate the middle 99% of the distribution are Z1= -2.575 & Z2= 2.575.

33. 40.62

35. 56.16

37.

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

  1. The probability that a randomly selected chicken egg hatches in less than 20 days is .1587.
  2. The probability that a randomly selected chicken egg hatches in more than 22 days is .1587
  3. The probability that a randomly selected chicken egg hatches between 19 and 21 days is .4772
  4. Yes, it is unlikely that an egg would hatch in less than 18 days because the probablity that a chicken egg hatches in less than 18 days is .0013.

39.

  1. The probability that a randomly selected bag of Chips Ahoy contains between 1000 and 1400 chocolate chips is .8658.
  2. The probability that a randomly selected bag of Chips Ahoy contains less than 1000 chocolate chips is .0132.
  3. The percentage of Chips Ahoy cookies that have more than 1200 chocolate chips is 70.19%.
  4. The percentage of Chips Ahoy cookies that have less than 1125 chocolate chips is 12.30%.
  5. 96th percentile rank.
  6. 4th percentile rank.

41.

  1. The percent of human pregnancies that last more than 270 days is 40.13%.
  2. The percentage of human pregancies that last more than 250 days is 15.87%.
  3. The percentage of human pregnancies that last between 240 and 280 days is 75.90%.
  4. The probability that a randomly selected pregnancy lasts more than 280 days is .1894.
  5. The probability that a randomly selected pregnancy lasts no more than 245 days is .0951
  6. Very “preterm” babies are unusual. The probability of having a “very preterm” baby is .0043.

43.

  1. The proportion of rods that have a length less than 24.9cm is 7.64%.
  2. The proportion of rods that will be discarded is 3.24%.
  3. The plant manager should expect to discard 162 of the 5000 rods.
  4. 11,804 rods should be manufactured if the order states that all rods must be between 24.9cm and 25.1cm.

45.

  1. If the mean is 0, then the spreads are accurate for games in which a team is favored by 12 or fewer points.
  2. The probability that the favored team wins by 5 or more points is .3228
  3. The probability that the favored team loses by two or more points is .4286

47.

  1. The 17th percentile for incubation times of fertilized egss is 20 days.
  2. The incubation times for the middle 95% of fertilized eggs is between 19 and 23 days.

56. A person would score better on the SAT because their z score would be approximately 1.02 where the z score for the ACT is approximately .9608, which signifies a lower score.