SOLUTION: As manager of a company you know that the distribution of completion times for an assembly operation is a normal distribution with a mean of 120 seconds and a standard deviation of

Question 1133150: As manager of a company you know that the distribution of completion times for an assembly operation is a normal distribution with a mean of 120 seconds and a standard deviation of 20 seconds. If you have to award bonuses to the top 10% of your workers what time would you use as a cut-off time?
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
the z value for 0.90 is 1.282. Here, however, we want the people with the LEAST time needed, so we will use z=-1.282, since the top 10 workers will be at the left end of the curve for time.
z=(x-mean)/sd
-1.282=(x-120)/20
-25.64=x-120
x=94.36 seconds or fewer
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