# probability

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## probability

 Let {Xi} be a sequence of i.i.d random variables such that  Xi = 1with probability p      = 0 with probability 1 – p Define y = 1 if i=1to 100 ∑Xi= 100               =0 otherwise   then E(y^2)=   a) infinity b) n!/100! * (n-100)!  p^100 (1-p)^n-100 c) np d) (np)^2
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## Re: probability

 is this ques from a past year paper,? if yes please tell which year is it from?
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## Re: probability

 No Mauli, its not.
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## Re: probability

 In reply to this post by Devika If you could please check if the limit of ∑Xi is from (1 to 100) OR from (1 to n)?? If its the former I am getting my ans as p^100. For the latter case my answer is coming out to be option b. ---  "You don't have to believe in God, but you should believe in The Book." -Paul Erdős
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## Re: probability

 Heyy Sinistral. Yes, its summation 1 to n. Sorry for the mistake. Your answer is right. Option b. Explain please?