8.1

15 (a) The x bar is normal with ?? = 80, standard deviation= 2.

  1. The possibility of x bar greater than 83 is 0.0668.

  2. The possibility of the x bar less and equals to 75.8 is 0.0179.

  3. The possibility of the x bar greater than 78.3 and less than 85.1 is 0.7969.

17

  1. The population must be normally distributed to compute probabilities involving the sample mean. If the population is normally ditributed, then the sampling distribution of x bar is also normally distributed with ??=64 and standard deviation =4.907

  2. The possibility of the x bar less than 67.3 is 0.7486

  3. The possibility of the x bar greater and equals to 65.2 is 0.4052

19

  1. The possibility id x less than 260 is 0.3520

  2. The smapling distribution of x bar is normal with m=266 and standard deviation =3.578

  3. The possibility of the x bar less and equals to 260 is 0.0465

  4. The possibility of the x bar less and equals to 260 is 0.0040.

  5. The outcome is unusual, so the sample likely came from a population whose mean gestation period is less than 266 days.

  6. The possibility of x bar greater and equals to 256 and less and equals to 276 is 0.9844.

21

  1. P(x>95)=0.3085

  2. P(x bar>95)=0.0418

  3. P(x bar>95)=0.0071

  4. increasing the sample size decreases P(x bar>95). This happens because standard deviation decreases as n increases.

  5. A mean reading rate of 92.8 wpm is not unusual since the possibility greater and equals to 92.8 is 0.1056.

  6. There is a around 5% chance that the mean reading spead of a random sample of 20 second-grade students will be greater than 93.7 words per mintue.

23

  1. p(x>0)= 0.5675

  2. p(x bar>0)=0.7291

  3. P(x bar>0)=0.8051

  4. P(x bar>0)=0.8531

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

8.2

11

  1. The sampling distribution of p hat is normal with ??=0.8 and standard deviation=0.046

  2. The possibility of p hat greater and equals to 0.84 is 0.1922.

(c)The possibility of p hat less and equals to 0.68 is 0.0047.

12

  1. the sampling distribution of p hat is normal with ??=0.65 and standard deviation=0.987

  2. the possibility of p hat greater and equals to 0.68 is 0.675

  3. the possibility of p hat is 0.0454

13

  1. The sampling distribution of p hat is normal with ??=0.35 and standard deviation=0.015.

  2. The possibility of p hat is greater and equals to 0.39 os 0.0040.

  3. The possibility of p hat less than and equals to 0.32 os 0.0233.

  1. the sampling distribution of p hat is normal with ??=0.35 and standard deviation=0.667

  2. P=0.0342

  3. P=0.745

15

  1. Qualitative with two possible outcomes-order a meal in a foreign language, or not.

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

  3. The sampling distribution of p hat is normal with ??=0.47 and standard deviation=0.035.

  4. P(p hat >0.5)=0/1977

  5. The possibility of p hat less than and equals to 0.4 os 0.0239.

  1. Quantitative. Either satisfied or not.

  2. the random sampling is the answers that those Americans have in their life.

(d). P=0.964

  1. it is pretty usual for a survey of 100 americans to reveal that 75 or fewer are satisfied with the way things are going on thier life. Becaus the possibility is higher than the 0.05.

17

  1. The sampling distribution of p hat is normal with ??=0.39 and stadard deviation=0.022.

(b)P( p hat<0.38)=0.3228

(c)P(0.4<p hat< 0.45)=0.3198

  1. the possibility of p hat greater and equals to 0.42 is 0.0838.