SOLUTION: The Empirical Rule is often used to set process control criteria. The idea is to accept some variation in the output of the process but to specify 'triggers' for further investigat

Question 1122170: The Empirical Rule is often used to set process control criteria. The idea is to accept some variation in the output of the process but to specify 'triggers' for further investigation or intervention.
You are the manager of a plant producing pipes for drainage and sewage applications. Pipes are supposed to have a diameter of 400mm and it is assumed that the diameters of pipes actually produced by the process follow a Normal distribution (the Normal curve) with mean 400mm and standard deviation 2mm.
If a quality control inspection finds a pipe more than 402mm or less than 398mm in diameter, production is halted and the plant is overhauled. Using the Empirical Rule, what proportion of pipes are between 398mm and 402mm in diameter? Select the best answer from the list below.
Select one:
a. 0.5
b. 0.997
c. 0.68
d. 0.95
Thanks very much
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
The range 398 to 402 is +/- 1 sd from the mean of 400. z=(x-mean)/sd=2/2 or 1.
This would be 68.3% so best answer is
C.

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