Talk:Cramér's V

What should be the level of importance/class?[edit]

Importance - I wasn't sure what to use here. Since some places online say that Cramer's V is the most popular measure of association for nominal data - I thought this article should get more then just "low" importance. But I'm not sure if this is correct or not.
Class - I put class as "start" (and not a stab) since the article has (IMHO) more content then to be a stab.

I'd be happy to read your opinions Talgalili (talk) 12:15, 22 January 2011 (UTC)[reply]

When was Cramer's V first proposed?[edit]

I searched and wasn't able to find the reference citing the first time that Cramer's V was proposed. Can someone please help out with that? Talgalili (talk) 12:15, 22 January 2011 (UTC)[reply]

Update: I found a hint here: http://www.jstor.org/stable/2577276 That it was published in Cramer's book from 1946 (Cramer, H. 1946. Mathematical Methods of Statistics. Princeton: Princeton University Press.) but I am not sure that is the case (since I don't have access to this book). Talgalili (talk) —Preceding undated comment added 12:40, 22 January 2011 (UTC).[reply]

Try googling the book's title + 'pdf' and trying a few links. The legality of such sites may be dubious, but personally when a book is over 50 years old and the author is deceased, I don't feel too many moral qualms. Don't add a link to such a site though. --Qwfp (talk) 18:39, 22 January 2011 (UTC)[reply]

ToDo for this article[edit]

Adding an example
Finding out how to calculate the signif of the coefficient (maybe it's the one of the chi squared test - but it needs to be cited) — Preceding unsigned comment added by Talgalili (talk • contribs) 16:56, 22 January 2011 (UTC)[reply]

Agree an example would be useful. I'm sure Pearson's chi-squared test is the relevant way to get a p-value as Cramer's V is based on Pearson's chi-squared statistic, but I don't have a citation.--Qwfp (talk)

Hi Qwfp, I added the claim about the P value (it's also something I've heard from one of the statistics doctors in our department, but I still feel this is something that could benefit from a citation).

Regarding an example, I see that even the Pearson's_chi-squared_test doesn't really have a proper example of independence. Once it will (which I won't get to do at this moment), I'll get to add it here, while implementing Cramer's V to it.

Thanks again for having a look at this. Talgalili (talk) 19:56, 22 January 2011 (UTC)[reply]

Bias correction, ommission? Not sure if this is the place to do this, but I think there is a mistake in the bias correction from Bergsma. If I understand the original article (google and a pdf will appear) I notice the denominator in V~ shows not min(k-1,r-1), but min(k~-1,r~-1), both k~ (or c~ in the original) and r~ are defined in the article: r~ = r - (r-1)^2/(n-1) and c~ = c - (c-1)^2/(n-1). Not sure if I'm overlooking something in that article but perhaps someone can have a quick look at it. — Preceding unsigned comment added by 194.171.35.201 (talk) 16:40, 9 March 2016 (UTC)[reply]

goodness-to-fit[edit]

As per the article, k>1, r=1 when used against goodness-to-fit. However that leads to ${\sqrt {\frac {x^{2}/n}{0}}}$ which isn't defined. Needs either an example or a citation. — Preceding unsigned comment added by 72.76.179.171 (talk) 19:43, 31 December 2015 (UTC)[reply]

Hi there,

1) I didn't find the source for this claim, I just cited some other non-reliable source. But the logic makes sense to me.

2) It should be (I think) sqrt(chi^2 / n*(k-1))

Trying this for: x = c(50, 50) vs probabilities of 0.5,0.5 Gives a cramer's v of 0; x = c(80, 20)

Gives a cramer's v of 0.6; x = c(100, 0) Gives a cramer's v of 1; Which makes sense to me. Here is some R code to reproduce:

x <- c(80, 20)
n <- sum(x)
chi <- chisq.test(x)$stat
sqrt(chi / n)

x <- c(100, 0)
n <- sum(x)
chi <- chisq.test(x)$stat
sqrt(chi / n)

x <- c(50, 50)
n <- sum(x)
chi <- chisq.test(x)$stat
sqrt(chi / n)

Please add your remarks to the talk page - in the hopes someone in the future will add more resources.

With regards, Tal Galili (talk) 12:19, 4 January 2016 (UTC)[reply]

I ultimately deleted the mention of this version of Cramér's V, per the "no original research" rule, as there's no reliable source for it (in addition to no evaluation through simulations, no peer review, etc.. It might be an unreliable effect size in certain situations and potential users wouldn't know it). 85.169.195.108 (talk) 15:46, 21 May 2023 (UTC)[reply]