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S2 help

Wonder if anyone could be kind enough to help me ... revising for S2 retake on Tuesday and haven't done any stats since June :s-smilie:

With continuous random variables, they give you a function e.g.

x/15 7 < x < 10
0 otherwise

And to find the E(X) you have to integrate x f(x). That's fine. But what do you do when there's more than one function? Which do you integrate, or is it both?

Any help much appreciated.
Reply 1
emmings
Wonder if anyone could be kind enough to help me ... revising for S2 retake on Tuesday and haven't done any stats since June :s-smilie:

With continuous random variables, they give you a function e.g.

x/15 7 < x < 10
0 otherwise

And to find the E(X) you have to integrate x f(x). That's fine. But what do you do when there's more than one function? Which do you integrate, or is it both?

Any help much appreciated.


Say your given a pdf of

f(x) a < x < b
g(x) c < x < d

Then E(x) = Integral of x.f(x) between a and b, + Integral of x.g(x) between c and d.

Galois.
Reply 2
Galois
Say your given a pdf of

f(x) a < x < b
g(x) c < x < d

Then E(x) = Integral of x.f(x) between a and b, + Integral of x.g(x) between c and d.

Galois.


Thanks very much

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