The hatcheck staff has had a long day, and at the end of the party they decide to return people’s hats at random. Suppose that npeople have their hats returned at random. We previously showed that the expected number of people who get their own hat back is 1, irrespective of the total number of people. In this problem we will calculate the variance in the number of people who get their hat back.Let Xi= 1if the ith person gets his or her own hat back and 0 otherwise. Let Sn::= n i=1 Xi, so Snis the total number of people who get their own hat back. Show that (a) E [Xi2] = 1/n.

MATLAB: An Introduction with Applications
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ISBN:9781119256830
Author:Amos Gilat
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Chapter1: Starting With Matlab
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The hatcheck staff has had a long day, and at the end of the party they decide to return people’s hats at random. Suppose that npeople have their hats returned at random. We previously showed that the expected number of people who get their own hat back is 1, irrespective of the total number of people. In this problem we will calculate the variance in the number of people who get their hat back.Let Xi= 1if the ith person gets his or her own hat back and 0 otherwise. Let Sn::= n i=1 Xi, so Snis the total number of people who get their own hat back. Show that (a) E [Xi2] = 1/n.

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