# An unnoticed mechanical failure

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An unnoticed mechanical failure has caused one-fourth of a machine shop’s production of 10,000 pistol firing pins to be defective. A random sample of 25 firing pins was drawn from the population. a.) Explain why this random variable has a binomial distribution? (2 points) b.) What are the mean and the standard deviation of the random variable? (2 points) c.) Find P(X > 4). Use the binomcdf function on your calculator. (2 points) Is it appropriate to use the normal approximation to the binomial for this problem? Support your answer with numbers and a test. Using the normal approximation with the continuity correction, calculate the probaility that you'll observe more than 4 defective firing pins in the random sample of 25. Indicate the X values and the z scores involved. How does your answer compare with the one you have in part c? How do you account for the difference in parts c and e? And sketch the probability distribution and the area you found using the normal approximation with the continuity correction.

d) Is it appropriate to use the normal approximation to the binomial for this problem? Support your answer with numbers and a test.

e) Using the normal approximation with the continuity correction, calculate the probaility that you'll observe more than 4 defective firing pins in the random sample of 25. Indicate the X values and the z scores involved.

f)How does your answer compare with the one you have in part c?

g)How do you account for the difference in parts c and e?

h)And sketch the probability distribution and the area you found using the normal approximation with the continuity correction.

- 10 years ago

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### MATHS - An unnoticed mechanical failure has caused one-fourth of a machine shop’s

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