Thread: Calculate E[X] and Var[X]

Question : Calculate E[X] and Var[X] when X represents the outcome when a fair die is rolled.
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Originally Posted by zorro

Question : Calculate E[X] and Var[X] when X represents the outcome when a fair die is rolled.
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Substitute f(x) and the values of x into the formulas that you have quoted and do the calculations.

Please show all your work if you're still stuck.

I am getting the following results

E[X] =

Var[X] = 3.07 .................Is that correct???

E(x)=3.5

Originally Posted by zorro

Question : Calculate E[X] and Var[X] when X represents the outcome when a fair die is rolled.
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i think you should try to make a probability
x | f(x)
1 | 1/6
2 | 1/6
: | :
: | :
6 | 1/6

then use the formula:



hope it help....

Originally Posted by zorro

I am getting the following results

E[X] =

Var[X] = 3.07 .................Is that correct???

I think you know now that the first is not correct (I haven't checked the second).

When I say:

Please show all your work if you're still stuck.

I don't mean that you simply show the results of your work. I mean show all the work. If you had done this, it (probably) would have been simple to point out the mistake you made. Post #5 shows what I expected you to post when I said:

Substitute f(x) and the values of x into the formulas that you have quoted and do the calculations

thanks mite
cheers