8.1

15

  1. Sample mean is approximately normal with a mean of 80 and a standard deviation of 2.

  2. 0.0688

  3. 0.0179

  4. 0.7969

17

  1. The population must be normally distributed so we can compute probabilities involving the sample mean. If the population is normally distributed, the sampling distribution of the sample mean is also normally distributed. Sample mean’s mean would be 64 and the standard deviation would be 4.907.

  2. 0.7486

  3. 0.4052

19

  1. 0.3520

  2. The sample distribution of the sample mean is normal with a mean of 266 and a standard deviation of 3.578.

  3. 0.0465

  4. 0.0040

  5. The result would be unusual, so we could conclude that the sample came from a population with a mean gestation period shorter than 266 days.

  6. 0.9844

21

  1. 0.3085

  2. 0.0418

  3. 0.0071

  4. Increasing the sample size decreases the probability of sample mean being more than 95 wpm. This is because the standard deviation of the sample mean decreases as n increases.

  5. 92.8 wpm is not an unusual mean reading rate because the probability of sample mean being larger than 92.8 wpm is 0.1056. This means the new program isn’t profusely more effective than the old.

  6. 93.7 wpm

23

  1. 0.5675

  2. 0.7291

  3. 0.8051

  4. 0.8531

  5. The probability of earning a positive rate of return increases as investment time horizon increases.

8.2

11

  1. The sampling distribution of the sample population is approximately normal with a mean of 0.8 and a standard deviation of 0.046.

  2. 0.1922

  3. 0.0047

12

  1. The sampling distribution of the sample population is approximately normal with a mean of 0.65 and a standard deviation of 0.046.

  2. 0.2578

  3. 0.0968

13

  1. The sampling distribution of the sample population is approximately normal with a mean of 0.35 and a standard deviation of 0.015.

  2. 0.0040

  3. 0.0233

14

  1. The sampling distribution of the sample population is approximately normal with a mean of 0.42 and a standard deviation of 0.0129.

  2. 0.0102

  3. 0.0606

15

  1. Qualitative, and there are 2 possible options. Either they can order or cannot.

  2. The source of variability is the individuals in the survey and their ability to order a meal in a different language.

  3. The sampling distribution of the sample population is approximately normal with a mean of 0.47 and a standard deviation of 0.035.

  4. 0.1977

  5. The probability of %40 or less people having the ability to order food in a different language is 0.0239, or about 2 people out of 100. This is unusual.

16

  1. Qualitative, and there are 2 possible options. Either they are happy or not.

  2. The source of variability is the individuals in the survey and if they are happy or not.

  3. The sampling distribution of the sample population is approximately normal with a mean of 0.82 and a standard deviation of 0.038.

  4. 0.2119

  5. The probability of %75 or fewer people being happy is 0.0329, or about 3 people out of 100. This is unusual.

17

  1. The sampling distribution of the sample population is approximately normal with a mean of 0.39 and a standard deviation of 0.022.

  2. 0.3228

  3. 0.3198

  4. The probability of %42 or more people thinking marriage is obsolete is 0.0838, or about 8 people out of 100. This is not unusual.