Math Is Fun Forum

Kenshinofkin

Member

Registered: 2008-07-08

Posts: 6

Probability questions (what formulas do I use)

Could someone help me with these problems. I am not sure what formulas to use. Thanks

A company produces component parts for an engine. Parts specifications suggest that 95% of items meet specifications. The parts are shipped to customers in lots of 100.

a) What is the probability that more than 2 items will be defective in a lot?
b) What is the probability that more than 10 items will be defective in a lot?

The turkeys found in a particular county have an average weight of 15.6 pounds with a standard deviation of 4.0 pounds. Forty-five turkeys are randomly selected for a county fair.

a) Find the probability that the average weight of the turkeys will be less than 14.5 pounds.
b) What is the probability that the average weight of the turkeys will be more than 17 pounds?
c) Find the probability that the average weight of the turkeys will be between 13 and 18 pounds.

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Probability questions (what formulas do I use)

For the first question, the exact answer would need the binomial distribution Bin(100, 0.05).
(Where a 'success' is defined as a part being defective)

However, as the amount of trials is high and the probability of success is low, the distribution can be approximated by a much simpler Poisson distribution. P(5) should approximate the above binomial distribution closely enough.

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Why did the vector cross the road?
It wanted to be normal.