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From | Janet Hill <janethill73@yahoo.co.uk> |
To | statalist@hsphsun2.harvard.edu |
Subject | RE: st: RE: Re: Kenel density function |
Date | Tue, 29 Jun 2010 18:54:56 +0000 (GMT) |
Sorry for my ineptitude explaining the data. The master and cast are scanned and the scanner has a fixed increment of 0.25 mm (the smallest that can be obtained) so I have binned data at these increments and I wanted to see how 'reproducible' the scans were. Eventually, so I have just found out, the experiment will extend to comparing 3 different methods of of making the cast. So my final analysis is going to compare 3 methods when the outcome is a frequency distribution - if that is possible. Many thanks for your time. 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: RE: st: RE: Re: Kenel density function > To: statalist@hsphsun2.harvard.edu > Date: Tuesday, 29 June, 2010, 15:36 > 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 > > > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ > * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/