SOLUTION: The diameters of steel disks produced in a plant are normally distributed with a mean of 2.5 cm and standard deviation of .02 cm. ---10 % of the disks with the highest diameters

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Question 1157816: The diameters of steel disks produced in a plant are normally distributed with a mean of 2.5 cm and standard deviation of .02 cm.
---10 % of the disks with the highest diameters are recycled .find the lowest diameter of such disks …………………………………
HINT: What value marks the 90th percentile of this distribution?

Answer by Boreal(15235)   (Show Source): You can put this solution on YOUR website!
The z-value for 90th percentile is +1.282
z=(x-mean)/sd
1.282=(x-2.5)/0.02
0.0256=x-2.5
x=2.5256 or 2.526 cm

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