The following table shows the probability distribution for a discrete random variable.
X 13 16 18 21 23 25 26 31
P(X) 0.07 0.21 0.17 0.25 0.05 0.04 0.13 0.08
The mean of the discrete random variable X is 20.59. What is the variance of X? Round your answer to the nearest hundredth.

- anonymous

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- anonymous

http://math.elon.edu/statistics112/prob_dist.html

- anonymous

\[s2 = Σ ( x _{I} - x )2 / ( n - 1 )\]

- anonymous

are you there??

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- anonymous

yes

- anonymous

can you explain the equation a bit?

- anonymous

sure lets star with \[\sum_{i=1}^{n}\]

- anonymous

do you understand what this means?

- anonymous

yes

- anonymous

good then\[x_{i} -x\] xi is each value of your x value .
-x really i cant use xbar because the keyboard is limited .. x bar is the average= \[xbar=\sum_{i=1} x _{i}/n\]

- anonymous

we are assuming that you have sample and not population as well !!!!

- anonymous

alright..I'm a little lost now

- anonymous

tell me where.

- anonymous

at the last part you posted

- anonymous

"we are assuming that you have sample and not population as well"
that

- anonymous

yes and before that

- anonymous

look. inorder to help you you need to be clear as to where are you not understanding . so i can help you better. thanks

- anonymous

I'm sorry, I just don't understand it.

- anonymous

no need to be sorry . :)

- anonymous

have you done statistics before ?

- anonymous

no, but this is in my algebra 2 work

- anonymous

thats cool/

- anonymous

do you now how to get the mean?

- anonymous

yes

- anonymous

ok so were half way.

- anonymous

lets talk concept first. is that ok?

- anonymous

sure

- anonymous

variance is the distance from the mean measured in squares. |dw:1343956195413:dw|

- anonymous

in you r case you have many data points. so really your job is fine all the distance from the mean and then sum them up and divide by the number of data point and minus 1.

- anonymous

s2=Σ(xI−x)2/(n−1) thats what this formula say.

- anonymous

oh alright

- anonymous

share what your thinking if you like?

- anonymous

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