# Math Help - Random Variable Simple Help Needed !!!

1. ## Random Variable Simple Help Needed !!!

I am trying to solve the following problem, but not sure if i am doing it right, I know the the answer for B is right...but A and C not sure yet.........The question is as follow...
A computer code consists of two blocks written independently by two programmers. Each block contains no errors with probability 0.6, one error with probability 0.3, and two errors with probability 0.1.

a)What is the probability that there are more errors in the first block than in the second block?

b)What is the probability that two blocks have an equal number of errors?

For this part i got .46 = (.6^2) + (.3^2) + (.1^2)

c)Compute the expected number of errors in the 1st block.

2. Let $X_i$, $i=1,2$ be the number of errors in the $i$th block, i.e., $P(X_i=0)=0.6$, $P(X_i=1)=0.3$ and $P(X_i=2)=0.1$. Then the answer to (a) is $P((X_1=1\mbox{ and }X_2=0)\mbox{ or }(X_1=2\mbox{ and }X_2=0)\mbox{ or }(X_1=2\mbox{ and }X_2=1))$. Your answer to (b) is correct. The answer to (c), i.e., the expectation of $X_1$ is $0\cdot P(X_1=0)+1\cdot P(X_1=1)+2\cdot P(X_1=2)$.

3. Hey, Thanks for the clarification, got it, thanks alot...