Talk:Velocity dispersion

Statistical dispersion specifics

This is too vague.

>is the statistical dispersion of velocities about the mean velocity

Statisticians use several different measures of dispersion: the range, the standard deviation, the variance, the interquartile range. There's no indication of which one of these is used in astronomy as the velocity dispersion. Blaise (talk) 18:55, 6 April 2013 (UTC)

Clicking around to some of the related articles, it definitely is not the variance which would have SI units of m^2/s^2; most of the units in those articles seem to be m/s. Can't help much further than that. --Izno (talk) 20:16, 17 September 2015 (UTC)

I think the velocity dispersion squared is the average of the radial velocity squared of all observed stars in a cluster or galaxy. See e.g. [1]. That would imply it is standard deviation, which also uses sigma as symbol so that seems plausible. But I'm not 100% sure this is the official definition. Gap9551 (talk) 21:30, 17 September 2015 (UTC)

Second paragraph

The second paragraph starts with "This relationship takes several forms..." but it's not clear what relationship we are talking about, since no mention of any relationship was made prior to that sentence. AxelBoldt (talk) 23:05, 16 September 2015 (UTC)

I rephrased it a bit. Gap9551 (talk) 21:26, 17 September 2015 (UTC)

"our pwn poor group"

the linked article doesn't have the word 'poor' in it anywhere. Perhaps the language of that article - Group 0, to Group 5, would be better. --2607:FEA8:D5DF:1AF0:89E4:B3DB:7CD7:65FD (talk) 11:31, 9 October 2020 (UTC)