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| rev | Admin | (Created page with "'''Solution: C''' Let <math>N</math> be the number of boys. Clearly <math>N \leq 1 </math>. If <math>N=0 </math> then we have three girls and the probability of this event is (1/2)<sup>3</sup>. Hence the probability distribution for <math>N</math> is <math>P(N=0) = 0.125, P(N=1) = 0.875 </math>. Then <math>E[N] = 0.875 </math> and <math>E[N^2] = E[N] = 0.875 </math> and the variance equals 0.875 - 0.875<sup>2</sup> = 0.109375.") | Jun 25'24 at 3:59 | +431 |