# CQE Exam Probability question - help needed

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#### RACHJAIS

1) An inspection plan is set up to to randomly sample 3ft^2 of a 1000 ft^2 carpet and to accept the carpet if no flaws are found in the 3 ft^2 sample. is the probability that a roll of carpet with an average of 1 flaw per square foot will be rejected by the plan? Answer is 0.95.... How do u solve it?

2) A process is in control with a defect rate of 0.2%. A sampling plans calls for 30 items to be
selected at random, and for the process to be shut down and corrected if any defects are found. How
often will the process be shut down without a change in the defect rate ?
A. 1.22% of the time B. 5.83% of the time C. 3.91% of the time D. None of the above

I would really appreciate if someone could help me out with the solutions... The exam is this coming saturday

D

#### debyang

Re: CQE exam probability question- help needed

Both questions can be resolved by using Execl function Poisson distribution.
Q1. mean=1/ft^2x3ft^2=3, accept Pr =POISSON(0,3,true)=0.049787, reject Pr=1-accept Pr=1-0.049787=0.95

Q2.mean=0.2%x30=0.06, no defect Pr=POISSON(0,0.06,true)=0.941765,
defect found Pr=1-0.941765=0.058235=5.823%

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#### RACHJAIS

Re: CQE exam probability question- help needed

for the first question: To calculate the mean; n= 3 and P = 1??? thas how u calculated the mean?
I appreciate ur help!

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#### debyang

Your question is stated that "an average 1 flaw per sq ft.

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