Census data show that in 1970, there were 203 million people in the U.S., of whom 9.8% were 65 or older. In 1990, there were 249 million people, of whom 12.5% were 65 or older. Is the difference in the percentages statistically significant? Select one: O a. More information is needed. b. Yes, it is statistically significant. O c. Yes, it is statistically significant at a =5% level. d. No, it is not statistically significant. OO e. The arithmetic of a two-sample z-test is easy enough to do, but the result is close to meaningless