Final answer:
Sample A, with 38 successes out of 40, provides the most significant evidence for the claim that the proportion is greater than 0.75, while Sample D, with 27 out of 40 successes, provides no evidence for the claim.
Step-by-step explanation:
A hypothesis test to see if the proportion of US citizens who can name the capital city of Canada is greater than 0.75 is conducted using various sample results. When comparing Sample A (38 successes out of 40) to Samples B (31 out of 40), C (34 out of 40), and D (27 out of 40), Sample A provides the most significant evidence for the claim because it has the highest proportion of successes (38/40 = 0.95), which is substantially greater than 0.75.
On the other hand, Sample D (27 out of 40 = 0.675) provides no evidence for the claim since its success rate is less than 0.75. Therefore, Sample D is actually evidence against the claim that the proportion is greater than 0.75.
A hypothesis test could be a test of means or proportions. Considering we're dealing with success rates, this is a test of proportions. When the data involve categorizing into 'success' or 'failure' and we must infer about a population proportion, a test of proportions is used.