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Test 4(2) - confidence interval for the population mean...

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ECO 222 Test 4 Name________________________ 12/2/1011; due Monday, 12/5 1. Eighty-four shoppers were interviewed at random, and 51 said that they prefer to shop alone rather than with someone such as friends or family. A. Let p represent the proportion of all shoppers at this mall who would prefer to shop alone. Find a point estimate for p . B. Find a 90% confidence interval for p . C. How many more shoppers should be included in the sample to be 90% sure that a point estimate will be within a distance of 0.05 from p ? D. Suppose p= .5 is the average for shoppers to shop alone, would you say that shoppers who prefer to shop alone has increased based on your random sample of 84 shoppers for a level of significance of α = .01? 2a. How healthy are the employees at Direct Marketing Industry? A random sample of 12 employees was taken, and the number of days each was absent for sickness was recorded (during a 1-year period). Use these data to create a 95%
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Unformatted text preview: confidence interval for the population mean days absent for sickness. 2 5 3 7 10 6 8 5 11 3 1 Since σ is unknown, a student – t table should be used. b. If the same confidence interval is used, how many employees should be in the random sample so that there is no more than 1 sick day of error? c. If Direct Marketing Industry, found that the national average for sick days is 6.5 days, are their employees healthier than the national average or can the company only assume they had a good year? Use α=.01 3. The average salary for a person in the business field on Long Island is $67,452, with a standard deviation, = $1,326. If you wanted to select the top 9 companies to apply for a job, what would the average salary of the top 9 companies have to be to be greater than $67,452 at α = .01. Compare that to a level of significance of α = .05. What would your opinion be comparing the 2 significance levels....
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