Mechanical: Predicting Probability of Manufacturing Flaws


An inspection sampling plan is set up to randomly sample 4 meters from a roll of 220 meters of plastic coated wire and to accept the wire roll if no flaws are found in the 4 meter length. What is the probability that a wire roll with an average of 0.8 flaws per meter will be rejected by the plan?


The solution to this problem requires a knowledge of the Poisson Probability Model and of the rules of probability:

Applying the Poisson Probability Model:

P(0 flaws) = P(accept the roll using the sampling plan) =

Applying the complement rule:

P(reject the roll using the sampling plan) = 1 - P(0 flaws) = 1 - 0.0408 =0.9592

There is a 96% chance that a roll with as many as 0.8 flaws/meter will be rejected by this sampling plan.

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Written by Louise Routledge, Tuesday, June 24, 1997