please help me a.s.a.p (by tomorrow)

[maths_arghh234]

i need help with how to do this question, i don't even know where to start. i'm gettin relly stressed ova it :\ ... the probability that a mass produced item will be defective is 0.01. find the distribution of the number of defectives in a random sample of two of the items... plzz help !!!

 

[DrLee]

i need help with how to do this question, i don't even know where to start. i'm gettin relly stressed ova it :\ ... the probability that a mass produced item will be defective is 0.01. find the distribution of the number of defectives in a random sample of two of the items... plzz help !!!

In a random sample of 2 items, there are only 3 possibilities -- there can be 0, 1, or 2 defectives

The probability of 0 defectives is (1-.01) * (1-.01) = .9801

The probabilty of 2 defectives is .01 * .01 = .0001

And the probability of exactly 1 defective is (.01 * .99) + (.99 * .01) = 2*.0099 = .0198

That's the distribution ... and we note that the sum of the 3 probabilities = 1.0000 as it should.

 

[maths_arghh234]

thank u soo much !!