ex_0530

# ex_0530 - these customers. You find that the average time...

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Exercise on May30 1. (7.23) We concern the annual earnings of hourly-paid workers at National Bank. The following is the earnings of a random sample of 20 white female workers: 25,249 19,029 17,233 26,606 28,346 31,176 18,863 15,904 22,477 19,102 18,002 21,596 26,885 24,780 14,698 19,308 17,576 24,493 20,612 17,757 Give a 95% confidence interval for the mean annual earnings of all white female hourly workers at this bank. 2. Example of One Sample t Problem. Your business needs to purchase three new copiers. Specifically, the company is interested in finding a copier that has excellent maintainability standards, for example, the average time it takes to repair a machine when it is down. The company that has the best

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price claims their average repair time is 1 hour . You plan to order the copiers from this company unless you find evidence that their claim is false. Before placing an order for the copiers you acquire a random sample of 20 customers who are currently using their machines and collect data from
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Unformatted text preview: these customers. You find that the average time to repair is 1.25 hours with a standard deviation of .75 hours . Should you order the copiers? 3. Exercise 7.3 on page 436 4. Exercise 7.7 on page 439 5. (7.76) Two sample t significance test and confidence interval: Does cocaine use by pregnant women cause their babies to have low birth weight? To study this question, birth weights of babies of women who tested positive for cocaine during a drug screening test were compared with the birth weights for women who either tested negative or were not tested, a group we call “other.” Here are the summary statistics. The birth weights are measured in grams: Group n x bar s Positive Test 134 2733 599 Other 597 4 3118 672 a) Formulate appropriate hypotheses and carry out the test of significance for these data? b) Give a 95% confidence interval for the mean difference in birth weights. 6. Exercise 7.78 on page 485 part a 7. Exercise 7.62 on page 481 8. Exercise 7.73 on page 483...
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## This note was uploaded on 02/27/2008 for the course BCOR 1020 taught by Professor Liang,fang during the Summer '07 term at Colorado.

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ex_0530 - these customers. You find that the average time...

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