Difference between revisions of "Talk:Precision Models"
(Created page with "Herb 4/19/2015 (1) I'd rename this page "Models for Precision". (2) "We have four options for measuring and analyzing precision:" Wrong. There are zillions of options. (3)...") |
m (David moved page Talk:Measuring Precision to Talk:Precision Models without leaving a redirect) |
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Revision as of 16:02, 22 April 2015
Herb 4/19/2015
(1) I'd rename this page "Models for Precision".
(2) "We have four options for measuring and analyzing precision:" Wrong. There are zillions of options.
(3) "General Bivariate Normal" is not "The normal, a.k.a. Gaussian, distribution." Is it a two dimensional distribtion which is somewhat analgous to the one dimensional distribution.
Symmetrical meaning SD(V) = SD(H) vs Unsymmetrical meaning SD(V) <> SD(H)
Correlated meaning ρ <> 0, vs Uncorrelated meaning ρ = 0.
So there are 4 cases.
Symmetrical Uncorrelated Bivariate Normal is a special case known as Rayleigh Distribution.
(4) Statistical Analysis of Dispersion / "(1) The Closed Form Precision model requires that we assume the shot group is, or can be normalized to be, a fairly symmetric bivariate Gaussian process, but allows for the most convenient estimators and analysis. Therefore, whenever σx≈σy we prefer this approach. "
This is just wrong. "Closed form" means that integrals of the PDF exists so that a CDF can be calculated. The Radial Standard Deviation is a closed form model, Extreme Spread (aka group size) is not.
(5) Statistical Analysis of Dispersion / "(2)Circular Error Probable disregards any ellipticity in the actual shot process in order to characterize precision using a single parameter."
Not really true. Circular Error Probable assumes no ellipticity. If you apply model incorrectly and get burned then that is your problem, not a fault of the model.
(5) Statistical Analysis of Dispersion / "(4)Extreme Spread and the other Range Statistics, which increase with group size n, do not have any useful functional forms."
First group size is used incorrectly again here to mean the Number of shots per group. Second there are not any "Closed Forms" for the distributions. So functions must be evaluated via Monte-Carlo sampling rather than integrated. "Functional forms" is an undefined concept.
(6) Overall I'd remove "Statistical Analysis of Dispersion" and "Tools" section from page if renamed to "Models For precision."
(7) If page was renamed to be for models, then I add section for Error Propagation and move that discussion from "What is Precision?" page here.
