RE: st: RE: Re: Kenel density function

["Nick Cox" <n.j.cox@durham.ac.uk>]

You can smooth binned data: the problem, if any, is in over-interpreting
results. 

Where does the binning come from? Why aren't unrounded data available? 

Nick 
n.j.cox@durham.ac.uk 


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Janet Hill
Sent: 29 June 2010 15:23
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: RE: Re: Kenel density function

Thank you for that. There is a single master and 6 separate impressions
have been taken of this so they are uncoupled. The difference between
each impression and the master has been measured and this gives the
binned data.Ideally this should have a value of zero for perfect fit. I
thought that I could use the kernel density on binned data but I
obviously need to do some more reading.

Any advice would be gratefully received.

Janet
--- On Tue, 29/6/10, Nick Cox <n.j.cox@durham.ac.uk> wrote:

> From: Nick Cox <n.j.cox@durham.ac.uk>
> Subject: st: RE: Re: Kenel density function
> To: statalist@hsphsun2.harvard.edu
> Date: Tuesday, 29 June, 2010, 14:54
> You should tell us more about the
> design. Do these come in groups of six, or are the six
> distributions entirely uncoupled from each other? It sounds
> as if that information has been omitted from what you have;
> if so, retrieving it is the first priority. 
> 
> Either way, trying to reduce all this to Kolmogorov-Smirnov
> looks severely problematic to me. As the data are already
> binned, kernel estimation also looks suspect. 
> 
> Nick 
> n.j.cox@durham.ac.uk
> 
> 
> Janet Hill
> 
> I would be grateful for some advice. I have some data from
> an experiment in which the difference between a cast and the
> master model has been measured. The data consists of the
> frequency of difference from -8 to + 8 mm in steps of 0.25,
> and 6 different casts were made. Kernel density plots show
> obvious differences between the casts but is there any way I
> can formally test this - or am I missing an obvious way to
> compare the frequency distributions/ I had thought of using
> Kolmogorov-Smirnov followed by multiple comparisons but I
> was not sure how applicable it would be.
> 
> I am using Stata 11.1
> 

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