Question

3. A poll result shows that among 150 randomly selected adults, 57 approved the job of the president of United States. (a) Can we say that exactly 38% of Americans approved the job of the president? Explain briefly. (b) Determine the 95% confidence interval for the approval rate of the president’s job in United States. (c) Suppose 400 adults are randomly selected and interviewed, and 38% of them approved the president’s job. Determine the 95% confidence interval of the approval rate. (d) Suppose 1,000 adults are randomly selected and interviewed, and 38% of them approved the president’s job. Determine the 95% confidence interval of the approval rate. (e) If you wish to reduce the size of the 95% confidence interval to 4% or less (i.e., 38%±2% or smaller), at least how many people should be interviewed? Describe what you did to get your number.

Answer 1