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anonymous
 4 years ago
random variable x s properties(i)the mean of X is 2. and (2) the mean of x^2 is 9.what is variance of 4x?
anonymous
 4 years ago
random variable x s properties(i)the mean of X is 2. and (2) the mean of x^2 is 9.what is variance of 4x?

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amistre64
 4 years ago
Best ResponseYou've already chosen the best response.0for a population\[Var=\frac{\sum (xX)^2}{n}\] hmmm

amistre64
 4 years ago
Best ResponseYou've already chosen the best response.0thats all I can come up with at the moment :/

amistre64
 4 years ago
Best ResponseYou've already chosen the best response.0what does it mean: the mean of x^2 = 9?

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0hey try the options for the ques are80,20,144,112

amistre64
 4 years ago
Best ResponseYou've already chosen the best response.0i know that much :) i just dont know what the sentence itself means

amistre64
 4 years ago
Best ResponseYou've already chosen the best response.0if we add up all the x^2s and divide by how many there are we get 9 perhaps?

amistre64
 4 years ago
Best ResponseYou've already chosen the best response.0(xX)^2 = x^2 2xX + X^2 \[Var=\frac{\sum x^2}{n}\frac{\sum 2xX}{n}+\frac{\sum X^2}{n}\] might be useful if its correct

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0hey how did u get this?

amistre64
 4 years ago
Best ResponseYou've already chosen the best response.0i expanded the (xX)^2 and split the fraction

amistre64
 4 years ago
Best ResponseYou've already chosen the best response.0now, I believe the sum of x^2/n is the mean of x^2

amistre64
 4 years ago
Best ResponseYou've already chosen the best response.0\[Var=\frac{\sum x^2}{n}\frac{\sum 2xX}{n}+\frac{\sum X^2}{n}\] \[Var=9\frac{\sum 2x(2)}{n}+\frac{\sum (2)^2}{n}\] \[Var=9\frac{\sum 4x}{n}+4\] \[Var=13\frac{\sum 4x}{n}\] is what im guessing so far

amistre64
 4 years ago
Best ResponseYou've already chosen the best response.0now, \[\sum_{1}^{n} 4x=4\sum_{1}^{n}x=4(x_1+x_2+x_3+...+x_n)=4xn\]

amistre64
 4 years ago
Best ResponseYou've already chosen the best response.0thats wrong; \[4\sum_{1}^{n} x=\frac{4n(n+1)}{2}=2n(n+1)\]

amistre64
 4 years ago
Best ResponseYou've already chosen the best response.0divided by n = 2n+2 var = 13  2n + 2 var = 15  2n but that doesnt seem to be applicable as an answer tho

amistre64
 4 years ago
Best ResponseYou've already chosen the best response.0well, class is starting so I gots to go; good luck :)

amistre64
 4 years ago
Best ResponseYou've already chosen the best response.0I want to say its 20. to recap: a mean is an average, an average is adding up all the values and dividing by how many there are. \[avg(x_1,x_2,x_3,...,x_n)=\frac{x_1+x_2+x_3+...+x_n}{n}=\frac{\sum x}{n}=\mu\] given that:\[\mu=2;\ and\ \frac{\sum(x^2)}{n}=9\]what is variance of 4x? From algebra we know that (xu)^2 can be expanded to: x^2 2xu + u^2\[\frac{\sum (x\mu)^2}{n}=\frac{\sum (x^22x\mu+\mu^2)}{n}=\frac{\sum(x^2)}{n}\frac{\sum(2x\mu)}{n}+\frac{\sum(\mu^2)}{n}\] replace this with known values: \[9\frac{\sum(2x*2)}{n}+\frac{\sum(2^2)}{n}\] constants can be factored out and the average of a constant is itself \[94\frac{\sum(x)}{n}+4\] relpace known values \[94*2+4=5\] \[var(x)=5\] we want to know the variance of 4 times x which I would say is 4*5 = 20 but i reserve the right to be complety wrong :) \[94\frac{\sum(x)}{n}+4\]

amistre64
 4 years ago
Best ResponseYou've already chosen the best response.0i dont know why the last part is tacked on the end .... but its just spurious.
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