Harper’s Index claims that 23% of people in the U.S. are in favor of outlawing cigarettes. You decide to test this claim and ask a random sample of 200 people in the U.S. whether they are in favor of outlawing cigarettes.

Of the 200 people, 27% are in favor of outlawing cigarettes. At a .02 level of significance, is there enough evidence to reject the claim?

Solution: We have to use a z-test of proportions. The statistics is:

The critical value for a 0.02 level of significance is 2.33, which means we cannot reject the null hypothesis that claims that 23% of people in the U.S. are in favor of outlawing cigarettes.

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