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    Z-Test for Mean, Z-Test for Proportion, ANOVA

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    Exercises 6 (Ch. 10) ,pg 344 - The MacBurger restaurant chain claims that the mean waiting time of customers is 3 minutes with a population standard deviation of 1 minute. The quality-assurance department found in a sample of 50 customers at the Warren Road MacBurger that the mean waiting time was 2.75 minutes. At the .05 significance level, can we conclude that the mean waiting time is less than 3 minutes?

    Exercises 28 (Ch. 11), pg 397 - Each month the National Association of Purchasing Managers publishes the NAPM index. One of the questions asked on the survey to purchasing agents is: Do you think the economy is expanding? Last month, of the 300 responses, 160 answered yes to the question. This month, 170 of the 290 responses indicated they felt the economy was expanding. At the .05 significance level, can we conclude that a larger proportion of the agents believe the economy is expanding this month?

    Exercises 34 (Ch. 12), pg 442 There are four auto body shops in Bangor, Maine, and all claim to promptly serve customers. To check if there is any difference in service, customers are randomly selected from each repair shop and their waiting times in days are recorded. The output from a statistical software package is:

    Summary
    Groups Count Sum Average Variance
    Body Shop A 3 15.4 5.133333 0.323333
    Body Shop B 4 32 8 1.433333
    Body Shop C 5 25.2 5.04 0.748
    Body Shop D 4 25.9 6.475 0.595833

    ANOVA
    Source SS df MS F p-value
    Between Groups 23.37321 3 7.791069 9.612506 0.001632
    Within Groups 9.726167 12 0.810514
    Total 33.09938 15

    Is there evidence to suggest a difference in the mean waiting times at the four body
    shops? Use the .05 significance level.

    Exercises 26 (Ch. 17), pg 665
    26. A study regarding the relationship between age and the amount of pressure sales personnel feel in relation to their jobs revealed the following sample information. At the .01 significance level, is there a relationship between job pressure and age?

    Degree of Job Pressure
    Age (years) Low Medium High
    Less than 25 20 18 22
    25 up to 40 50 46 44
    40 up to 60 58 63 59
    60 and older 34 43 43

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    Solution Summary

    The solution provides step-by-step method of performing Z-test for Mean, Z-Test for Proportion and ANOVA. All the steps of hypothesis testing (formulation of null and alternate hypotheses, selection of significance level, choosing the appropriate test-statistic, decision rule, calculation of test-statistic and conclusion) have been explained in details. A separate Excel sheet showing the ANOVA analysis has also been included.

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