2. Suppose 10 people toss their hats into a box and then take turns drawing hats at random, so each person ends up with one hat. How many possible permutations of the hats are there? Assume that each such permuation is equally likely. Let Si be one if the ith person gets her own hat, zero otherwise. (a) Calculate mean and variance of Si. (b) Calculate the covariance of Si and S; when i + j. (c) Let S be the number of people who get their own hat. Calculate the mean and variance of S.

A First Course in Probability (10th Edition)
10th Edition
ISBN:9780134753119
Author:Sheldon Ross
Publisher:Sheldon Ross
Chapter1: Combinatorial Analysis
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Problem 1.1P: a. How many different 7-place license plates are possible if the first 2 places are for letters and...
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2. Suppose 10 people toss their hats into a box and then take turns
drawing hats at random, so each person ends up with one hat. How many
possible permutations of the hats are there? Assume that each such
permuation is equally likely. Let Si be one if the ith person gets her own
hat, zero otherwise.
(a) Calculate mean and variance of Si.
(b) Calculate the covariance of S; and S; when i + j.
(c) Let S be the number of people who get their own hat. Calculate the
mean and variance of S.
Transcribed Image Text:2. Suppose 10 people toss their hats into a box and then take turns drawing hats at random, so each person ends up with one hat. How many possible permutations of the hats are there? Assume that each such permuation is equally likely. Let Si be one if the ith person gets her own hat, zero otherwise. (a) Calculate mean and variance of Si. (b) Calculate the covariance of S; and S; when i + j. (c) Let S be the number of people who get their own hat. Calculate the mean and variance of S.
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