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This seems like a simple question, but I am unsure. Please bear with me and thanks for the help.

I am told to suppose that A,B are discrete random variables that have a joint pdf, and am told to calculate the marginal and conditional 'pdfs'. I thought that a probability density function was associated with continuous random variables, so is it just a typo when the question says calculate the pdf? Is it is really just calculating the marginal 'pmf'?

Thanks.

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    $\begingroup$ From a measure theoretic viewpoint, there is not difference. The pmf (probability mass function) is a probability density function (pdf) with respect to the counting measure, that is, the measure that puts weight one on every object in the discrete set. $\endgroup$
    – Xi'an
    Commented Mar 6, 2021 at 15:11
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    $\begingroup$ @Xi'an is absolutely correct but, from a non-rigorous point of view ( in case you didn't take measure theory ), you can just think of it as that they left out the term "discrete" and they really meant "discrete probability density function" or "discrete probability mass function". $\endgroup$
    – mlofton
    Commented Mar 6, 2021 at 20:25

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