1. The problem statement, all variables and given/known data Question 3 here: http://www.stat.washington.edu/peter/395/samplemidterm.pdf [Broken] Solution to it here: http://www.stat.washington.edu/peter/395/prmt.sln/sln.html [Broken] By the way, I could use help soon since this is the practice exam for an exam I'm taking 7 hours from now!!!! 2. Relevant equations Bienayme-Chebyshev inequality: P(|X-E(X)|>t) ≤ Var(X) / t2 3. The attempt at a solution So I'm just confused at how he gets the expected value. He multiplies the chance of choosing a first pair of students to be boy and girl by 100 .... which doesn't make sense since with each successive choosing of pairs the probability of choosing boy and girl depends on whether the last pair choice happened to be boy and girl. Also, on the solution to problem 1 he says "Assuming the density is defined on x>1 ...." How would I have known this on an exam????