A poll conducted March 6-8, 2004 by the Wall Street Journal/NBC News asked a random sample of 1018 respondents their opinions about gay marriage. When asked to state whether they would favor or oppose a "constitutional amendment making it illegal for gay couples to marry," 43% responded in favor of the amendment and 52% opposed (5% were unsure). When these same respondents were asked whether they would favor or oppose a "constitutional amendment that defined marriage as a union between a man and a woman and made same-sex marriages unconstitutional," 54% favored the amendment, 42% opposed (1% said it depends, and 3% were not sure).
A friend suggests carrying out a two-sample z-test of proportions to compare these results. What is the primary reason why this would not be an appropriate analysis of these data?