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Simone Werner

Simone Werner

Answered question

2022-05-31

MathJax(?): Can't find handler for document MathJax(?): Can't find handler for document Consider probability spaces ( Ω , G , P ) and ( Ω , F , Q ) with the properties F G and P | F = Q.
Let X be a Q-integrable (and F -measurable) random variable. Is it true, that
E P [ X ] = E Q [ X ] ?
I feel like this should be true. I think there is an approximation of X with simple functions on F and because of the fact, that P ( F ) = Q ( F ) for any F F .

Answer & Explanation

coquinarq1

coquinarq1

Beginner2022-06-01Added 14 answers

It is true. In fact, it is true when 0 X is F-measurable, which then implies it is true for integrable F-measurable X since X = X + X −. To prove for 0 X , you can prove it for simple functions on F and then take a sequence of nonnegative simple functions ϕ n X and use the monotone convergence theorem.

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