Definition talk:Expectation

I have mostly encountered $\mathrm E$, $\mathbb E$ or $\mathbf E$ for $E$, and I like them better. Thoughts? --Lord_Farin (talk) 09:36, 16 October 2012 (UTC)


 * All my notes use $E$. It's easier. Please don't use $\mathbb E$, I would prefer if bb was reserved for sets of numbers. --Jshflynn (talk) 12:43, 16 October 2012 (UTC)


 * While $E$ is easier, it obfuscates the distinction between variables and operators, always a dangerous thing to do IMO. --Lord_Farin (talk) 12:50, 16 October 2012 (UTC)


 * I am yet to encounter $E$ being used as a variable (at least off the top of my head). I vote bf should you wish to carry this out. It has also occurred to me lately that the theorem section of many theorem pages contain sentences such as "where blah denotes the blah of blah". This is obviously primarily because symbols exceed concepts in count but I wonder whether or not it would be a good idea on the new German ProofWiki to have a "notation setup" section within each theorem page so that the theorem statement is clearer. Thoughts? --Jshflynn (talk) 13:22, 16 October 2012 (UTC)


 * Good call. I checked my source work and it actually has $\mathsf E$, which would work for me. Completely agree with Jshf about bb, and I don't like bf as that sounds like a vector / matrix to me. Similarly $\mathsf {VAR}$ would be used for variance. --prime mover (talk) 19:44, 16 October 2012 (UTC)


 * The mathsf font is fine with me as well. --Lord_Farin (talk) 20:09, 16 October 2012 (UTC)

It seems like this page is missing something. Let's say, for example, we have $X \sim \operatorname U[0 \,.\,.\, 1]$, and a function $f$ as follows: $$\displaystyle f(x) = \begin{cases} x & x \lt \frac 1 2 \\ 3/4 & x \ge \frac 1 2 \end{cases}$$ Now, the distribution $f(X)$ is neither discrete nor continuous, but intuitively it does have an expectation of $\frac 1 2$.


 * And so exactly why should that missing thing be on this page in particular? --prime mover (talk) 09:58, 9 March 2019 (EST)