So, im in an online stats class where we don't get much guidance obviously but sometimes i really need it and the teacher is unwilling to help because she believes self-teaching is the best method.
only thing is, this is already graded, the final exam is this week, & no matter how hard i try.. i still don t understand this problem?
this is the problem :
18% of high school boys and 10% of high school girls say they rarely or never wear seat belts. Suppose one high school boy and one high school girl are selected at random, with the random variable of interest being the number in the pair who say they rarely or never wear seat belts. Describe two ways of finding the expected value and standard deviation of this random variable, at least approximately.
my response:
The first way is if you let the random variable x=how many of the two people wear a seat belt then x=0,1,2
Find the probability distribution p(x) of x and calculate the expected value with an exponential function such as Exp(x + y)=E(x) + E(y)
E(x) represents ln x which is an inverse of the log function.
And finally, the second way is if x is the random variable of the boy and y for the girl then x=0 or 1 and y=0 or 1
teachers response to me :
Answer this question using the probabilities that are given to you in the original discussion board entry. I'm having a hard time following this, and I don't see that you've addressed standard deviation.
okay.. so how do i answer this the right way?!!?!?