The report "Wireless Substitution: Early Release of Estimates from the National Health Interview Survey" (Center for Disease Control, 2009) gave the following estimates of the percentage of homes in the United States that had only wireless phone service at 6-month intervals from June 2005 to December 2008.
a. Construct a time series plot for these data and describe the trend in the percent of homes with only wireless phone service over time.
b. Has the percent increased at a fairly steady rate?