1. The problem statement, all variables and given/known data The second problem in thispic http://www.imagestation.com/picture/sraid220/p4c1709bad2d17fb97ea36c875b20474c/ebc1f71f.jpg [Broken] 2. Relevant equations Second problem: For bernoulli trials, if Sn= x1+x2+...+xn is the number of successes, then E(Sn)=np, V(Sn)=npq, D(Sn)=square root of V(Sn) 3. The attempt at a solution For the 2nd problem I have: A.) I do not know what they mean by common distribution. Sj = x1+x2+x3+x4+...+xj Expected value of Xj= sum of (Xj) * probability of (Xj) Variance = (j-1)*(probability of (Xj)) * (1 - probability of (Xj)) Standard deviation is the square root of variance B.) E(Tn)= n * P(Tn) V(Tn) = n * P(Tn) * (1-P (Tn)) C.) For coin tossing: E(nth occurance of head) = n * (1/2) V(nth offucence of head) = n * (1/2) * (1/2) I really am not sure about my work. I have been trying it all day. Any guidance would be helpful. Thank you.