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I have seen in a variety of contexts that they write "E(X) < ∞". What does it mean? My guess is that it means that E(X) is

__finite__, but if this is the case, shouldn't they say -∞ < E(X) < ∞ instead?

Also, I have seen the notation of the letter "d" above the equal sign. What does it mean? e.g.

d

X=F(Y)

[the "d" should be above the equal sign, not above X]

Does anyone have any idea or have seen the above notation?

Thanks for any help!