# Talk:Variance

From Encyclopedia of Mathematics

Should it be $\operatorname{Var}X$ or $\operatorname{D}X$ ? Moreover I think that $\xi$, $\zeta$ is more appropriate for random variables then $X$, $Y$. What do you think? --Nikita2 (talk)

- Yes, $\operatorname{Var}X$, as noted in the "Comments". About $\xi$, $\zeta$ I am neutral; also $X$, $Y$ are OK with me. --Boris Tsirelson (talk) 08:55, 23 February 2013 (CET)

What about mathematical expectation symbol? How should we type it? I found this $\mathbb{E}$ but I think is should be like E. --Nikita2 (talk) 06:01, 25 February 2013 (CET)

- Yes, E ($\mathsf{E}$, $\mathrm{E}$, $E$) are widely used. Also $\mathbb{E}$ is used. --Boris Tsirelson (talk) 07:44, 25 February 2013 (CET)

- As far as I understand, Ulf (our chief editor) does not try to enforce a uniform style on all our editors.
- However, here is what we can do. Put near the beginning of the article something like
- $\newcommand{\Ex}{\mathsf{E}}$
- and then write $ a = \Ex(X) $ etc. (Look at my wikitext in the edit mode to see what I mean.) This way it will be easy to replace all expectation symbols at once if one will want to do so in a future. --Boris Tsirelson (talk) 08:12, 25 February 2013 (CET)

**How to Cite This Entry:**

Variance.

*Encyclopedia of Mathematics.*URL: http://encyclopediaofmath.org/index.php?title=Variance&oldid=29486