9.1

25.

  1. .181

  2. The sample is less than 5% of the population and np(1-p) equals 341.8, which is greater than or equal to 10.

  3. The lower bound equals 0.168 and the upper bound is 0.194.

  4. We are 90% confident that the proportion of American adults who have donated blood in the past 2 years is between 0.168 and 0.194.

26.

  1. 0.430

  2. The sample is less than 5% of the population and np(1-p) equals 282.6, which is greater than or equal to 10.

  3. The lower bound equals 0.401 and the upper bound is 0.459.

  4. We are 95% confident that the proportion of workers and retirees in the US 25 years of age and older who have less than $10,000 in savings is between 0.401 and 0.459.

27.

  1. 0.519

  2. The sample is less than 5% of the population and np(1-p) equals 250.4, which is greater than or equal to 10.

  3. The lower bound equals 0.488 and the upper bound is 0.550. We are 95% confident that the proportion of adult Americans who believe thar televisions are a luxery are between .488 and .550.

  4. It is possible that a supermajority of adult Americans believe that television is a luxery since it may not be in the confidence interval, and it is not likely.

  5. The lower bound equals 0.450 and the upper bound is 0.512.

28.

  1. o.75

  2. The sample is less than 5% of the population and np(1-p) equals 192, which is greater than or equal to 10.

  3. The lower bound equals 0.715 and the upper bound is 0.785.

  4. It is possible that the proportion of adult Americans aged 18 or older for which the issue of family values is extremely or very important in determining their vote for president below 70%, and it is not likely.

  5. The lower bound equals 0.215 and the upper bound is 0.285.

29.

  1. The lower bound equals 0.071 and the upper bound is 0.151.

  2. The lower bound equals 0.058 and the upper bound is 0.164.

  3. As the level of confidence increases, the margain of error increases as well.