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Re: st: CDF plot with normal probability axis


From   David Hoaglin <[email protected]>
To   [email protected]
Subject   Re: st: CDF plot with normal probability axis
Date   Thu, 14 Nov 2013 08:10:33 -0500

Thanks, Nick.

I didn't see a = 1/3 in the FAQ or the SJ articles, and the derivation
of it is interesting.

I agree that small differences in plotting position are unlikely to
make much difference.

You make a good argument for avoiding -qnorm- and -quantile-.

David Hoaglin

On Thu, Nov 14, 2013 at 7:54 AM, Nick Cox <[email protected]> wrote:
> Quite so. Choice of plotting position is discussed at some length in
> the FAQ I mentioned, which links to the literature, and in
> publications on my -qplot-  and its predecessor -quantil2- in the SJ
> and STB respectively.
>
> Naturally I am all in favour of using a better method rather than a
> weaker one, but I remain unconvinced that minute differences in
> plotting position either are discernible on a graph or have impact on
> decisions about data, so long as you are not working with very small
> samples. If you are, nothing much helps.
>
> Your bigger argument is with StataCorp, who wire i / (n + 1) into
> -qnorm- and (i - 0.5) / _N into -quantile- and don't allow variations.
> My quantile plotting programs have always allowed user choice of a in
> (i - a) / (n - 2a + 1).
>
> Nick
> [email protected]
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