Harris Interactive conducted a poll of American adults in August of 2011 to study the use of online medical information. Of the 1,019 randomly chosen adults, 60% had used the Internet within the past month to obtain medical information.

Use the results of this survey to create approximate 95% confidence interval estimate for the percentage of all American adults who have used the Internet to obtain medical information in the past month.

Calculate the 90% confidence interval.

Which confidence interval has the smaller margin of error? Why does this make sense?

Which confidence interval is more likely to contain the true percentage of all American adults who have used the Internet to obtain medical information in the past month? Why do you think so?