Today’s newspapers and magazines often report the findings of survey polls about various aspects of life. The Pew Internet & American Life Project (January 13–February 9, 2005) found that “63% of cell phone users ages 18-27 have used text messaging within the past month.” Other information obtained from the project included “random telephone survey of 1,460 cell phone users” and “has a margin of sampling error of plus or minus 3 percentage points.”Relate this information to the statistical inferences you have been studying in this chapter.
a. Is a percentage of people a population parameter, and if so, how is it related to any of the parameters that we have studied?
b. Based on the information given, find the 95% confidence interval for the true proportion of cell phone users who have used text messaging.
c. Explain how the terms “point estimate,” “level of confidence,” “maximum error of estimate,” and “confidence interval” relate to the values reported in the article and to your answers in part b.