et X denote the R.V. that equals the number of tails minus the number of heads when N fair coins are flipped.   A. What is the expected value of X?   B. Prove that the variance of X equals N.

A First Course in Probability (10th Edition)
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Chapter1: Combinatorial Analysis
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4. Let X denote the R.V. that equals the number of tails minus the number
of heads when N fair coins are flipped.
 
A. What is the expected value of X?
 
B. Prove that the variance of X equals N.
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