Question

A politician claims that a proposal for a new traffic law is broadly supported by both political parties and that a person from either political party is equally likely to support the proposed legislation. He cites two recent polls that said 70% of a random sample of 550 people from his political party supports the law, and 65% of a random sample of 420 people from the other political party supports the law. The 95 percent confidence interval for the difference in population proportions is (–0.010, 0.110). Based on the interval, is the politician’s claim justified?

Answer 1

Based on the 95% confidence interval for the difference in population proportion, there is convincing statistical evidence that he is correct

Explanation:

The proportion from the sample of people from his party that support the law = 70%

The number the members of the politicians political party that support the law = 550 people

The proportion from the sample of people from the other party that support the law = 65%

The number the members of the politicians political party that support the law = 420 people

The confidence level of the test = 95%

The given confidence interval for the difference in proportion, C.I. = (-0.010, 0.110)

Given that the 95% confidence interval for the difference in population proportion ranges from -0.010, to 0.110, it is 95% certain that 0 is among the likely difference in proportion between the two populations and therefore, there is sufficient statistical evidence to suggest that there is no difference in the proportion of the members of either political that support the proposed new traffic law.