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# Probability (DRV) watch

1. I have a few questions can anyone help?
1) Suppose 100 are subject to a blood test. They are out into groups of 10 and only one person tested to save time and money. If that one test is negitive, the one test will suffice for the whole group, if the test is positive, all 10 people will have to be tested, giving 11 tests in all. Assume probability of a test being positive for all people is p=0.01 for all people, independantly of each other.

a) what is the probability that the test of the pooled sample of ten will be positive?

b)Find the expected number of tests necessary for 100 people under this plan.

2)Suppose that X is a random variable with mean (mew) and standard deviation (sigma)>0

a) find the expected value E(X^2)

B) Consider the random variable X*=(X-(mew))/sigma find the expected value and the varience of X*
2. Have you managed to do any of it so far?
3. no im completely baffled!
sorry :<

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Updated: November 14, 2008
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