Question 1194651
.The U.S census Bureau (Annual social and economic supplement) collects demographics
concerning the number of people in families per household. Assume the distribution of the
number of people per households is shown in the following probability distribution table:
x P(x)
2 0.27
3
4 0.28
5 0.13
6 0.04
7 0.03
a) Show that P(x=3) = 0.25

Solution:
The total of the probabilities must be equal to 1.
Therefore, P(x=3) = 1-0.27-0.28-0.13-0.04-0.03= 0.25

b) Calculate the expected number (mean) of people in families per household in the United
States.
To calculate the mean, multiply each value of x by the corresponding probability and get the sum.
E(X) = 2*0.27+3*0.25+4*0.28+5*0.13+6*0.04+7*0.03=  {{{highlight(3.51)}}}

c) Compute the variance and standard deviation of the number of people in families per
household.

Calculate first the mean of {{{X^2}}} by multiplying the square of x by the corresponding probability, and get the sum.

{{{E(X^2) }}}= {{{(2^2)*0.27+(3^2)*0.25+(4^2)*0.28+(5^2)*0.13+(6^2)*0.04+(7^2)*0.03}}} = 13.97

The variance is equal to {{{E(X^2) - (E(X))^2}}} = {{{13.97-3.51^2}}} = {{{highlight(1.6499)}}}.

The standard deviation is equal to the square root of the variance which is {{{highlight(1.284484)}}} 

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