Talk:Logit

Log-odds

This is not the same thing as Log-odds. There should be a separate article for that. --Scottieb 20:02, 2 October 2006 (UTC)

What do you take to be the difference? The logit of a number p is the log-odds of any event whose probability is p. The difference would seem to be that the logit is the logit of a number, whereas the log-odds is the log-odds of an event. Is that what you had in mind? Michael Hardy 20:40, 2 October 2006 (UTC)

Could someone fix up the image size for the logit-plot. I don't have the time right now. SW

merge?

hi, i think this article should be merged with logistic regression. Pdbailey 03:19, 20 April 2006 (UTC)

I use this function quite often without doing logistic regression - better to merge logistic regression with Probit model --Henrygb 01:24, 23 April 2006 (UTC)

How about before merging probit and logistic regression, we clarify on both pages what the relationship is between them? Currently neither page explains the other. Cazort 23:03, 24 October 2007 (UTC)

Looking better

This article has improved much over the last few days. Two things I might suggest: 1) use the deleted hospital example as an example in the logistic regression article (the current Ax+B example is nothing more than an example of calculating the odds); 2) In History, distinguish between the logit proper, and the logit model, which I assume is another word for logistic regression. Comments welcome and encouraged. Baccyak4H (Yak!) 16:09, 13 June 2007 (UTC)

Needs more Explanation

This article does not give adequate explanation/justification for the use of the logit function. Why is it used? What compelling mathematical, physical, or philosophical reasons are there for its use, for example, its use in logistic regression? I think this page can only be viewed as a stub until it contains this sort of material so I am going to mark it as such. Cazort 18:47, 24 October 2007 (UTC)

I agree. Furthermore it would be interesting to know why it is called "logit". -- 129.247.247.240 (talk) 08:31, 6 April 2009 (UTC)

The Logit#History section tries to explain that. Not sure if it needs to be worded better or retitled? Qwfp (talk) 09:25, 6 April 2009 (UTC)

Pronunciation

I think the pronunciation given is "chiefly US". The "chiefly UK" pronunciation is "lodge-it" rather than "low-git". I'd add this but I don't speak IPA at all. Qwfp (talk) 15:09, 5 March 2008 (UTC)

OR, but the presumed analogies are probit, logarithm and logic --Rumping (talk) 11:21, 9 October 2009 (UTC)

Comparison with Probit

"As a result, probit models are sometimes used in place of logit models because for certain applications (e.g. in Bayesian statistics) implementation of them is easier."

Could probit and logit be reversed in this sentence? Logit is almost always going to be computationally easier than probit, and Bayesian statistics is computationally demanding, even today.

Another important difference with probit that is often considered, i.e. when deciding between regression models, is that the logistic distribution has thicker tails than the normal distribution. This is visible in the graphic but strikes me as worth of a comment, as it offers reasons to use a logit model beyond computational ones. — Preceding unsigned comment added by 192.17.144.249 (talk) 05:18, 1 August 2013 (UTC)

Assessment comment

The comment(s) below were originally left at Talk:Logit/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

It's more than a stub but we should try to answer User:Cazort's questions under Talk:Logit#Needs more explanation. Qwfp (talk) 15:35, 5 March 2008 (UTC)

Last edited at 15:35, 5 March 2008 (UTC). Substituted at 20:04, 1 May 2016 (UTC)

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The specific log function is ambiguous

I would have thought that the natural log, ln() would have been the correct choice but log implies base 10. Which should it be? — Preceding unsigned comment added by Yamex5 (talk • contribs) 22:28, 28 June 2021 (UTC)

Plot of logit(p) in the domain of 0 to 1, where the base of logarithm is e.

Mathematically, the logit is the inverse of the standard logistic function $\sigma (x)=1/(1+e^{-x})$

@Yamex5: Very good question. It seems logical that the logit transformation uses the inverse of e^x which is ln(x) and not log(x). The difference is only a proportional factor. Nevertheless, I believe you are perfectly right and I fixed it. Thanks for pointing out.

I think it is a terminology issue, meaning that some people use log for the logarithm in general, while others differentiate between log for base 10 and ln for base e. As you can seen in the logit graph which says f(x) = log(x/(1-x)) it can't be a base 10 logarithm, but is a base e logarithm. With x=0,09 the term x/(1-x) results in about 0.1; log(0.1) = -1 but ln(0.1) = -2.3 so it is obvious that the graph is about the natural logarithm to base e although it says log in the formula. --Gunnar (talk) 06:58, 5 September 2021 (UTC)

resolved. Rubber Duck (☮ • ✍) 16:02, 7 November 2021 (UTC)