week5 - 1. A recent report in BusinessWeek indicated that...

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1. A recent report in BusinessWeek indicated that 32 percent of all employees steal from their company each year. (Round z-score computation to 2 decimal places and your final answers to 4 decimal places.) If a company employs 50 people, what is the probability that: (a ) fewer than 11 employees steal? Probability (b ) more than 11 employees steal? Probability (c) exactly 11 employees steal? Probability (d ) more than 11 but fewer than 21 employees steal? Probability Explanation: a. .0475, found by: Then (10.5 – 16)/3.30 = -1.67, for which the area is .4525. Then 0.5000 – .4525 = .0475 b. .9131, found by (11.5 – 16)/3.30 = -1.36, for which the area is .4131. Then 0.5000 + .4131 = . 9131 c. .0394, found by (10.5 – 16)/3.298 = -1.67 and (11.50 – 16)/3.298 = -1.36. Then .4525 – .4131 = .0394 d. .8262, found by adding the area between z = -1.36 and z = 1.36. Then .4131 +.4131 = .8262 2. The mean of a normal probability distribution is 380; the standard deviation is 8.
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(a ) About 68 percent of the observations lie between what two values? Value 1 Value 2 (b ) About 95 percent of the observations lie between what two values? Value 1 Value 2 (c) Practically all of the observations lie between what two values? Value 1 Value 2 Explanation: a. 372 and 388 found by 380 1(8). b. 364 and 396 found by 380 2(8). c. 356 and 404 found by 380 3(8) 3. Best Electronics, Inc. offers a "no hassle" returns policy. The number of items returned per day follows the normal distribution. The mean number of customer returns is 10.0 per day and the standard deviation is 2.5 per day. (a ) In what percent of the days are there 7.5 or fewer customers returning items? (Round z-score computation to 2 decimal places and your final answer to 2 decimal places. Omit the "%" sign in your response.) Percent % (b ) In what percent of the days are between 13 and 15 customers returning items? (Round z- score computation to 2 decimal places and your final answer to 2 decimal places. Omit the "%" sign in your response.) Percent % (c) Is there any chance of a day with no returns? Yes, but very unlikely.
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Explanation: a. 15.87%, found by (7.5 – 10.0)/2.5 = – 1.00, then 0.5000 – .3413 = .1587 b. 9.23%, found by: (13 – 10.0)/2.5 = 1.20. Area is .8849 z = (15 – 10.0)/2.5 = 2.00. Area is .9772 The area between 13 and 15 is .0923, found by .9772 – .8849. c.
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This note was uploaded on 01/08/2012 for the course QM-2241 XTIB taught by Professor Stine during the Spring '09 term at Troy.

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week5 - 1. A recent report in BusinessWeek indicated that...

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