10.2 Means sd Unknown

# Xlsx millions of investors buy mutual funds some

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Unformatted text preview: e condenser broke down was recorded. Should the president retain supplier A? (See Condensers.xlsx) Hypotheses: H0: μA – μB ≤ 0 Ha: μA – μB > 0 Example Hypothesis Tests The president of a company that manufactures automobile air conditioners is considering switching his supplier of condensers, Supplier A, who prices its product 5% higher than supplier B. Because the president wants to maintain his company’s reputation for quality, he wants to be sure that supplier B’s condensers last at least as long as supplier A’s. He decides to retain supplier A if there is sufficient statistical evidence that supplier A’s condensers last longer on average than supplier B’s. In an experiment, 30 midsize cars were equipped with air conditions using type A condensers while another 30 midsize cars were equipped with type B condensers. The number of miles (in thousands) driven by each car before the condenser broke down was recorded. Should the president retain supplier A? (See Condensers.xlsx) Hypotheses: H0: μA – μB ≤ 0 Ha: μA – μB > 0 p-value approach: p > .10 critical value approach: tSTAT = 0.94 < tCRIT = 1.67 Therefore, do not reject null hypothesis—insufficient evidence to conclude that supplier A’s condensers last longer. Therefore, switch to To Try… 2. 3. Hypothesis Tests As the regional sales manager for BLK Foods, you want to determine whether the mean weekly sales of BLK Cola are the same when using a normal shelf location and when using an end-aisle display. To test the effectiveness of the end-aisle displays, you select 20 stores from the BLK supermarket chain that all experience similar storewide sales volumes. You then randomly assign 10 of the stores to sample 1 (normal shelf location) and 10 to sample 2 (end aisle display). The sales at the end of one week are shown in the MS Excel file BLK Cola.xlsx. Millions of investors buy mutual funds. Some funds can be purchased directly from financial institutions while others must be purchased through brokers, who charge a fee for this service. This raises the question, Can investors do better by buying mutual funds directly than by purchasing mutual funds through brokers? To help answer this question, a group of researchers randomly sampled the annual returns from mutual funds that can be acquired directly and mutual funds that are bought through brokers and recorded the net annual returns (see Mutual Funds.xlsx). Assuming that the standard deviations have been determined to be equal for the two, can we conclude at the 5% significance level that directly purchased mutual funds outperform mutual funds bought through brokers? To Try… As the regional sales manager for BLK Foods, you want to determine whether the mean weekly sales of BLK Cola are the same when using a normal shelf location and when using an end-aisle display. To test the effectiveness of the end-aisle displays, you select 20 stores from the BLK supermarket chain that all experience similar storewide sales volumes...
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## This document was uploaded on 03/05/2014.

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