q5spr2005_key4714 - Quiz 5 EMA 4714 - Materials Selection...

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Quiz 5 EMA 4714 - Materials Selection and Failure Analysis KEY Wednesday, March 30, 2005 1. [10 points] Two batches [10,000 pieces each] of self-tapping steel fasteners were received from a heat treating facility who claimed that one batch had been tempered for twice the time as the other. The paperwork had been misplaced and there was no way of knowing which batch was which. A series of hardness measurements performed on pieces selected at random from each batch resulted in data contained within the table to the right. For your convenience [provision of same being a prime driving force for my existence], I have calculated means and standard deviations for the two sets of sample data. Based on your statistical analysis, and using a level of significance [ α ] of 0.05, does the data allow a determination that the two batches were subjected to different tempering times? *************************************************************************** First, determine which test statistic to use: s 2 2 /s 1 2 = 6.95; from F tables, critical region for ν = 9 = 2.44 [ α = 0.05]: use Statistical Test 7, σ unknown and s 1 not equal to s 2 k = [s 1 2 /n 1 ]/[s 1 2 /n 1 + s 2 2 /n 2
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This note was uploaded on 10/19/2011 for the course EMA 4714 taught by Professor Staff during the Spring '08 term at University of Florida.

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q5spr2005_key4714 - Quiz 5 EMA 4714 - Materials Selection...

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