In order to judge the effectiveness of an advertising campaign for a certain brand of pretzel, a company obtained a simple random sample of 95 convenience store receipts the week before the ad campaign began, and found that 28 of them showed a purchase of the pretzels. Another simple random sample of 65 receipts was taken the week after the ad campaign, and 33 of them showed a pretzel purchase. Construct a 98% confidence interval for the difference between the proportions of customers purchasing pretzels before and after the ad campaign. Interpret the results. A marketing manager claims that the proportion of customers who purchased pretzels did not change after the ad campaign. Does the confidence interval contradict this claim?
In order to judge the effectiveness of an advertising campaign for a certain brand of pretzel, a company obtained a simple random sample of 95 convenience store receipts the week before the ad campaign began, and found that 28 of them showed a purchase of the pretzels. Another simple random sample of 65 receipts was taken the week after the ad campaign, and 33 of them showed a pretzel purchase. Construct a 98% confidence interval for the difference between the proportions of customers purchasing pretzels before and after the ad campaign. Interpret the results. A marketing manager claims that the proportion of customers who purchased pretzels did not change after the ad campaign. Does the confidence interval contradict this claim?
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