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Math Help - Is this true or false?

  1. #1
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    Is this true or false?

    Can I ask if this sentence is true or false?

    (1) If X and Y is not correlated, P(A)P(B) = P(A or B) [I guess it is false]


    (2) Any hypothesis testing can be applied or approached by using confidential interval problems. [I guess it is false]
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  2. #2
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    Re: Is this true or false?

    1) It is false. There is a simple counter example. If P(B)=1 and P(A)=0.5 then P(A or B)=1 and P(A)P(B)=0.5. The question did not state that A and B cannot occur at the same time so their probabilities can sum to be greater than 1.
    I think you might have misstyped P(A)+P(B) as P(A)P(B), if that is the case then it is also false, only if A and B are mutually exclusive P(A)+P(B) = P(A or B)
    2) Confidence intervals cannot be used if what you are dealing with is not quantitative.
    Last edited by Shakarri; April 27th 2013 at 03:09 AM.
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  3. #3
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    Re: Is this true or false?

    Thanks a lot! Have a great weekend
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  4. #4
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    Re: Is this true or false?

    I am sorry to bother you. But can I ask about 'Suppose two random variables X and Y are positively correlated, If X is above its mean, then Y is also above its mean'?
    It is similar to the previous question (negatively correlated).. Thanks a lot!
    Last edited by yanirose; April 27th 2013 at 12:46 PM.
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