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:There is no such convention - you can pick any symbol you like, of course. It is common practice to use the capital for the cdf, because it's the primitive of the df. I've seen phi in quantum mechanical books, but I've also seen f and rho. [[User:Gerbrant|Shinobu]] 22:58, 3 October 2006 (UTC)
:From ''all'' the literatures I have read, the pair of F and f was the convention. I don't mean to say that Φ and φ are wrong, but how can you be so sure to declare something else as a bold claim? Many different fields have different notational conventions, and we just have to accept it. [[User:Musiphil|Musiphil]] 07:03, 3 December 2006 (UTC)
:: Lest anyone be confused by the confused comments of {{ping|Thoreaulylazy}} and {{ping|Gerbrant}} a.k.a. Shinobu above:
::: <math> \Phi </math> is conventionally the c.d.f. of the standard [[normal distribution]];
::: <math> \varphi</math> is conventionally the p.d.f. of the standard [[normal distribution]];
::: <math> F_X(x) </math> (with a capital ''F'' and a capital subscript ''X'' and a lower-case argument ''x'') is conventionally the c.d.f. of the distribution of whichever random variable is denoted ''X'' in the context in which this notation appears;
::: <math> f_X(x) </math> (with a lower-case ''f'' and a capital subscript ''X'' and a lower-case argument ''x'') is conventionally the p.d.f. of the distribution of whichever random variable is denoted ''X'' in the context in which this notation appears;
:: Thoreaulylazy seems to have seen the first usage above and to have mistakenly thought it applies to distributions in general rather than only to the standard normal distribution. {{ping|Musiphil}} seems to be unaware of the first convention above. [[User:Michael Hardy|Michael Hardy]] ([[User talk:Michael Hardy|talk]]) 14:58, 23 December 2019 (UTC)
====This is a collapsed disctintion. One uses Phi for the normal distribution and phi for the normal density. These are reseved symbols for these purposes --- see any statistics book. One uses F and f fo the generic distributions and densities, but these are not reserved. In many books and papers one will find G g , H h etc. Each time the capital representing distribution and the lower case the density.
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