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What is the variance of this probability distribution? Round your answer to 3 decimal places. X 1.02 2.04 3.07 4.11 P(X) 0.24 0.25 0.28 0.23 Could you please break down. I also need to know how to get the standard deviation. Thank you for any help given.

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  • $\begingroup$ Do you know the formula for the variance of a distribution? $\endgroup$
    – Trurl
    Sep 25, 2014 at 23:54
  • $\begingroup$ yes and I have work it over and over. The mean is 2.56 $\endgroup$
    – barb
    Sep 26, 2014 at 1:25
  • $\begingroup$ and then I tried to work the formula. I do not know how to put the formula on here. As you can tell I am new at this. $\endgroup$
    – barb
    Sep 26, 2014 at 1:28

1 Answer 1

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$$\begin{align} Var(X)&=E(X^2)-E(X)^2\\ &=(1.02^2\times0.24+2.04^2\times0.25+3.07^2\times0.28+4.11^2\times0.23)-(1.02\times0.24+2.04\times0.25+3.07\times0.28+4.11\times0.23)^2\\ \end{align}$$

For part 2, look up "standard deviation" and "variance".

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  • $\begingroup$ This is how I did it $\endgroup$
    – barb
    Sep 26, 2014 at 14:10
  • $\begingroup$ I got ans. as 1.26 but it is wrong the book says it is 1.429. The mean is 2.56 = 6.554 and then I got 7.814 for the second part and when I subtract I get 1.26 $\endgroup$
    – barb
    Sep 26, 2014 at 14:14
  • $\begingroup$ Slight correction $\endgroup$
    – Dale M
    Sep 26, 2014 at 22:04

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