9.1

25.

  1. the point estimate is .1808

  2. 417(1-.1808) > 10 and the sample population size is less than 5 percent of the population

  3. lower fence = .1677 and upper fence = .1939

  4. this means that there is 90 percent confidence that the proportion of Americans older then 18 who have donated blood is between .1677 and .1939

26.

  1. the point estimate is .43

  2. 496(1-.43) > 10 and the sample size is less than 5 percent of the population size

  3. lower fence = .4014 and upper fence = .4585

  4. This means there is 95 percent confidence that the proportion of people 25 and older in the US with less than 10000 dollars in savings is between .4014 and .4585

27.

  1. The point estimate is .5194

  2. 521(1 - .5194) > 10 and 10 and the sample size is less than 5% of the population size

  3. lower fence = .4885 and upper fence = .5503

  4. it is possible, but it’s highly unlikely

  5. lower fence = .4491 and upper fence = .5109

28.

  1. the point estimate = .75

  2. 768(1-.75) > 10 and the sample size is less than 5% of the population size

  3. lower fence = .71516 and upper fence = .7848

  4. this is possible but not very likely

  5. lower fence = .2153 and upper fence = .2847

29.

  1. lower fence = .0708 and upper fence = .1513

  2. lower fence = .05821 and upper fence = .1639

  3. There is a larger margin of error with a larger confidence interval.