8.1

15

  1. Normal, Mean=80, Standard deviation=2

  2. P=.0668. About 7 of 100 samples will have a mean greater than 83.

  3. P=.0179 About 2 of the 100 samples will have a mean less than or equal to 75.8.

  4. P=.7969 About 80 of the samples will result in a mean thats between 78.3 and 85.1

17

  1. Must be normally distributed.

  2. P=.7486 About 75 of the samples will result in a mean that is less than 67.3.

  3. P=.4052 About 41 of the samples result in a mean that is greater than or equal to 65.2.

19

  1. P=.3520 About 35 of the pregnancies will last less than 260 days.

  2. Normal with a mean of 266 and a standard deviation of 3.578.

  3. P=.0465 About 5 of the samples result in a mean that is less than or equal to 260 days.

  4. P=.0040 About 4 of the samples result in a mean period of less than of equal to 260 days.

  5. Unusual.

  6. P=.9844 About 98 of the samples result in a mean that is between 256 and 276 days.

21

  1. P=.3085 About 31 of the students will read more than 95 words per minute.

  2. P=.0418 About 4 of the samples result in a mean that is more than 95 words per min.

  3. P=.0071 About 7 of the samples result in a mean that is that is more than 95 words per min.

  4. Decreases probability.

  5. P=.1056, it would not be unusual.

  6. 93.7

23

  1. P=.5675 About 57 of the months will have positive return rates.

  2. P=.7291 About 73 of the samples will result in a mean return rate that is positive.

  3. P=.8051 About 81 of the samples will result in a mean return rate that is positive.

  4. P=.8531 About 85 of the samples will result in a mean return rate that is positive.

  5. Positive return rate increases are investment time horizon increases.

8.2

11

  1. Normal, Mean=0.8, Standard deviation=.046

  2. P=.1922 About 19 out 0f 100 samples of size n=75 will result in 63 or more individuals with the characteristic.

  3. P=.0047 About 5 out of 1000 random samples of n=75 will result in 51 or fewer with the characteristic.

12

  1. Normal, Mean=0.65, Standard deviation=.034

  2. P=.1894 About 19 out of 100 samples.

  3. P=.2236 About 22 out of 100 samples.

13

  1. Normal, Mean=0.35, Standard deviation=0.015

  2. P=.0040 About 4 out of 1000 samples.

  3. P=.0233 About 2 out of 100 samples.

14

  1. Normal, Mean=0.42, Standard deviation=0.013

  2. P=.9898 About 98 out of 100 samples.

  3. P=.0606 About 6 out of 100 samples.

15

  1. Qualitative.

  2. The source of variability in each individual is their ability to order a mean in a foreign language.

  3. Normal, Mean=0.47, Standard deviation=0.035

  4. P=.1977 About 20 out of 100 will result in a sample where the amount of Americans who can order a meal in a foreign language is greater than 0.5.

  5. P=.0239. Yes, it would be unusual.

16

  1. Qualitative.

  2. The source of variability in each individual is whether they are satisfied with the way things are going in their lives or not.

  3. Normal, Mean=0.82, Standard deviation=0.04

  4. P=.7823 About 78

  5. P=.0344. Yes, it would be unusual.

17

  1. Normal, Mean=.39, Standard deviation=.022

  2. P=0.3228 About 32 out of 1– samples of n=500 adults will result in less than 38%

  3. P=0.3198 About 32 out of 100 random samples of n=500 adults will have between 40-45% of the who believe that marriage is obsolete

  4. P=.0838. No, it would not be unusual.