Wikipedia:Reference desk/Archives/Science/2017 November 25

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November 25

Edit on Chi-squared test

Was this edit correct? An IP user changed this formula at Chi-squared test#Pearson's chi-squared test

$\sum _{i=1}^{k}{m_{i}}=\sum _{i=1}^{k}{x_{i}}=n$

to

$\sum _{i=1}^{k}{m_{i}}=n\sum _{i=1}^{k}{p_{i}}=n$.

No source was provided; not sure if this is vandalism. Jc86035 (talk) 12:40, 25 November 2017 (UTC)

You should get better answers on the Math desk, and a source really is needed, but to my ignorant eye it appears this is what the text said. (i.e. that mi = npi, so the sum of mi = n*sum of pi, given that n is constant for all pi. Also, it makes sense that the sum of all pi = 1. So long as the IP didn't change the text I don't think it can be vandalism. What I can't tell you with confidence is whether the whole thing is right. Wnt (talk) 16:04, 25 November 2017 (UTC)

Both versions are correct. n is the total number of observations, so the observed numbers add up to n: $\sum x_{i}=n$. The expected numbers also have to add up to n, so they are in a way constructed to obey the first relation. But this is automatically taken care of by the normalisation of the probabilities, and that is expressed by the second version. Not sure which one is preferable in the article, maybe one could throw in $\sum x_{i}=n$ somewhere, then everything is there. --Wrongfilter (talk) 16:30, 25 November 2017 (UTC)

@Wrongfilter: Maybe combining the equations in the same <math> would be best? Jc86035 (talk) 11:23, 26 November 2017 (UTC)

I did something like that yesterday. --Wrongfilter (talk) 11:58, 26 November 2017 (UTC)

Soyuz Interior

I am wondering if there is a page or image or any other type of media that has all the Soyuz controls on it even if they are in Russian. Does any page exist? YuriGagrin12 (talk) 16:56, 25 November 2017 (UTC)

I googled "soyuz design" and various possibly useful images turned up. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:29, 25 November 2017 (UTC)

I should've been more specific, I was wondering about the controls for the Soyuz-MS, there are a lot of controls here however they are from past versions of the Soyuz. YuriGagrin12 (talk) 17:46, 25 November 2017 (UTC)

Going by the OP's name, would have thought he would have been well placed to send an email off to [1]. If he also explains that he has $10,000,000 sloshing around in his current bank account and would like to buy a return ticket to ISS. Like any good automobile sales folk, they may be falling over themselves to provided both images of the current Soyuz-MSS and it forthcoming replacement, (which will surly include this time, a CD player, Tom-Tom navigation system, Wi-Fi connectivity, and a charging socket for his iPhone). Aspro (talk) 18:36, 25 November 2017 (UTC)

@Aspro: Haha! Unfortunatley I do nyet have zat kind of money. But do you think Star City would actually give me them? YuriGagrin12 (talk) 19:08, 25 November 2017 (UTC)

If any origination is going to have up-to-date photographs and diagrams etc., is is going to be a training centre that trains the next generation. Email and ask for a 'name' you can contact in their Public relations department. This is what PR people are for. They can be surprising helpful and providing your requests are clear and focused (i.e., not wishy-washy) they will do what they can. If they can't provide what you desire, they may be able to point you in the direction where you can find this information. If one doesn't ask one doesn't get. Aspro (talk) 19:48, 25 November 2017 (UTC)

Please, find it here. Ruslik_Zero 20:19, 25 November 2017 (UTC)