From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.comp.tex.context/4262 Path: main.gmane.org!not-for-mail From: Johannes Huesing Newsgroups: gmane.comp.tex.context Subject: Re: xml support in context / mathml Date: Sun, 4 Mar 2001 21:26:45 +0100 Sender: owner-ntg-context@let.uu.nl Message-ID: <20010304212645.A1206@ruhrau.de> References: <3.0.6.32.20010119170436.015574c0@server-1> <3A6C45D8.3DE3269A@elvenkind.com> <3.0.6.32.20010122165419.00931aa0@server-1> Reply-To: johannes.huesing@ruhrau.de NNTP-Posting-Host: coloc-standby.netfonds.no Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: main.gmane.org 1035394941 24202 80.91.224.250 (23 Oct 2002 17:42:21 GMT) X-Complaints-To: usenet@main.gmane.org NNTP-Posting-Date: Wed, 23 Oct 2002 17:42:21 +0000 (UTC) Original-To: ntg-context@ntg.nl In-Reply-To: <3.0.6.32.20010122165419.00931aa0@server-1>; from pragma@wxs.nl on Mon, Jan 22, 2001 at 04:54:19PM +0100 Xref: main.gmane.org gmane.comp.tex.context:4262 X-Report-Spam: http://spam.gmane.org/gmane.comp.tex.context:4262 On Mon, Jan 22, 2001 at 04:54:19PM +0100, Hans Hagen wrote: > > Somehow, when i look at the specs, i cannot get by the feeling that some > important aspects have been overlooked -) > Hi Hans and all, I skimmed the examples in the MathML manual (which Hans distributed some printed copies of during the Dante meeting) and I have some remarks regarding the statistics examples on pp. 131 to 134. In the examples empirically gained values and their expectations are mistaken for one another. The first example (which spells in TeX as $\bar{x} = \frac1n\sum x_i$) is ok (the mean being the sum of the values over the observations divided by the number of obs). Statistic 2 is not really wrong ($\sigma(x)\approx\sqrt{\frac{\sum(x_i-\bar{x})^2}{n-1}$) but a bit weak: I would take the expectation of the right expression and put an equal sign between the two expressions. For statisticians, there is definitely the need for an element which would spell as an upright E which is strongly right associative so you could drop the parentheses around the X in E(X) or in E(sin X) (although I would rather put the parentheses around here) but not in E(XY). Physicists would put angle brackets around the argument and drop the E so the expectation tag is not uninteresting. The third example is plain wrong as it really messes up the theoretical value "variance" $\sigma^2 = \expectation((X-\expectation(X))^2)$ and its unbiased estimate $s^2$, which is equal to the term on the right (the square of the right expression in example 2) but only approxiamtely equal to the expression in the middle (so you have to swap the \approx and the = in the example). Moreover, I find the notation of overbarring a whole expression unusual (and inconsistent with the i index since you don't write $\bar{x}_i$ either) but I do not know of a notation other than $\frac1n\sum\cdots$ for that. And this notation has the disadvantage that it had to be flexible wrt the number of observations (n here). And thank you very much for the lift back to Duisburg: I managed to make it home from there before Linux was updated on the laptop :-). Hope you made it home safely. Greetings Johannes -- "Human Genome" may be a binary file. See it anyway?