A Pew Research study finds that 23% of Americans use only a cell phone, and no land line, for making phone calls (The Wall Street Journal, October 14, 2010). A year later, a researcher samples 200 Americans and finds that 51 of them use only cell phones for making phone calls.

a. Set up the hypotheses in order to determine whether the proportion of Americans who solely use cell phones to make phone calls differs from 23%.

b. Compute the value of the appropriate test statistic and the corresponding p-value.

c. At α = 0.05, are the sample data inconsistent with Pew Research's findings of 2010? What do the sample data suggest? P-56