# Thread: Is this true or false?

1. ## 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]

2. ## 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.

3. ## Re: Is this true or false?

Thanks a lot! Have a great weekend

4. ## 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!