I really need help on this question- I’ve been using the same method and getting correct answers but this one has stumped me; I have my exam tomorrow -.-
I’ll list the whole question;
5) A random variable X has the distribution B(5,0.25)
Ia) Find E(x)—did this no problem
Ib) P(X=2)---again no problem
ii) Two values of X are chosen at random. Find the probability that their sum is less than 2----here is the problem.
I thought you can either get a 1 then a 0 or a 0 then a 1.
So I calculated
P(X=0) = 0.75^5
P(X=1) = 5C1 * 0.25 *0.75^4
Hence my final answer = 2( 0.75^5 *0.396…) =0.188
(used the fraction, didn’t round)
But the answer is 0.244---why???
I’ll list the whole question;
5) A random variable X has the distribution B(5,0.25)
Ia) Find E(x)—did this no problem
Ib) P(X=2)---again no problem
ii) Two values of X are chosen at random. Find the probability that their sum is less than 2----here is the problem.
I thought you can either get a 1 then a 0 or a 0 then a 1.
So I calculated
P(X=0) = 0.75^5
P(X=1) = 5C1 * 0.25 *0.75^4
Hence my final answer = 2( 0.75^5 *0.396…) =0.188
(used the fraction, didn’t round)
But the answer is 0.244---why???