9.1

25.

  1. Point Estimate= 0.18

  2. 340.37 is greater than or equal to 10, and the sample is less than or equal to 5% of the population.

  3. (0.167, 0.193)

  4. We are 90% confident that the true proportion of adults Americans who have donated blood in the past two years is between 0.167 and 0.193.

26.

  1. The point estimate= 0.43

  2. 282.6 is greater than or equal to 10, and the sample is less than or equal to 5% of the population.

  3. (0.402, 0.458)

  4. We are 95% confident that the true proportion of workers and retirees in the U.S 25 yrs old and older who have less than $10,000 in savings is between 0.402 and 0.458.

27.

  1. Point estimate= 0.519.

  2. 250.39 is greater than or equal to 10, and the sample size is less than or equal to 5% of the population.

  3. (0.488, 0.55)

  4. No, because 60% isn’t accounted for in the cofidence interval. It’s outside of it.

  5. (0.45- lowerbound, 0.512- upperbound)

28.

  1. Point estimate= 0.75

  2. 192 is bigger than or equal to 10, the sample size is less than or equal to 5% of the population.

  3. (0.715, 0.785)

  4. No, it cannot be below 70% as that would be outside the confidence interval.

  5. (0.215- lowerbound, 0.285- upperbound)

29.

  1. (0.07, 0.15)

  2. (0.057, 0.163)

  3. By increasing the confidence interval, the interval itself becomes larger, so it then becomes essentially less precise.