Statistics Weston Materials problem

Statistics Weston Materials problem - z(29) = (29-32)/2 =...

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The accounting department at Weston Materials, Inc., a national manufacturer of unattached garages, reports that it takes two construction workers a mean of 32 hours and a standard deviation of 2 hours to erect the Red Barn model. Assume the assembly times follow the normal distribution. a. Determine the z values for 29 and 34 hours. What percent of the garages take between 32 hours and 34 hours to erect? b. What percent of the garages take between 29 hours and 34 hours to erect? c. What percent of the garages take 28.7 hours or less to erect? d. Of the garages, 5 percent take how many hours or more to erect? The z score tells you how many standard deviations above/below the mean your sample is. The formula is: z = (x-mu)/sigma In your problem, mu = 32, sigma = 2.
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Unformatted text preview: z(29) = (29-32)/2 = -1.5 z(34) = (34-32)/2 = 1 a. What percent of the garages take between32 hours and 34 hours to erect? using a z table (http://davidmlane.com/hyperstat/z_table.html): p(0 < z < 1) = 0.3413 = 34.13% b. What percent of the garages take between 29 hours and 34 hours to erect? using the z table again: p(-1.5 < z < 1) = 0.7745 = 77.45% c. What percent of the garages take 28.7 hours or less to erect? Get the z value: z = (28.7-32)/2 = -1.65 using the table: p(z < -1.65) = 0.0495 = 4.95% d. Of the garages, 5 percent take how many hours or more to erect? From the table, the z value we need is: 1.6449 Solve for x: 1.6449 = (x-32)/2 Multiply by 2: 2*1.6449 = (x-32) Add 32: x = 2*1.6449 + 32 x = 35.2898 hours...
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This note was uploaded on 05/10/2011 for the course STATS 202 taught by Professor Emil during the Spring '11 term at Aberystwyth University.

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Statistics Weston Materials problem - z(29) = (29-32)/2 =...

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