Re: st: Trimming data and statistics

["Akihito Tokuhara" <akitoku4@hotmail.com>]

Dear Maarten,

I understand what you explained, and that is partly why I said I am 
hesitated to interpret the result.

And partly, at least, in one context, if the majority of replies comes back 
at zero value, these values
might be considered (assumed) as some "constant" effect of some factors 
which may likely exist,
for example, errors, unresponse due to filters, etc. Therefore, under this 
assumption, if the sample
size is increased, the number of those values also increases, so the median 
won't change whether
the sample size changes or not. Now cutting part of the "constant" effect 
may reduce the
overwhelming impact of such "constant" effect so that the "responsive" part 
may be seen.

But even so, I tend to think that this argument is only suitable in very few 
contexts. If I am wrong,
it is not a surprise either.

Akihito
------------------------

> From: Maarten buis <maartenbuis@yahoo.co.uk>
> Reply-To: statalist@hsphsun2.harvard.edu
> To: statalist@hsphsun2.harvard.edu
> Subject: Re: st: Trimming data and statistics
> Date: Fri, 14 Apr 2006 22:21:11 +0100 (BST)
>
> Akihito:
> I am not surprised that the middel observation (median) moves if you remove 
> the bottom 5% and the
> top 10% of a distribution. The problem is how to justify it.
> HTH,
> Maarten
>
> --- Akihito Tokuhara <akitoku4@hotmail.com> wrote:
> > The fact is, when I test-trim the dataset, the median actually
> > moves away from zero.
>
> --- Akihito Tokuhara <akitoku4@hotmail.com> previously wrote:
> >> My way if to cut off completely all obs having values less than p5 and 
> all
> >> those having values bigger than p90.
>
> -----------------------------------------
> Maarten L. Buis
> Department of Social Research Methodology
> Vrije Universiteit Amsterdam
> Boelelaan 1081
> 1081 HV Amsterdam
> The Netherlands
>
> visiting adress:
> Buitenveldertselaan 3 (Metropolitan), room Z214
>
> +31 20 5986715
>
> http://home.fsw.vu.nl/m.buis/
> -----------------------------------------
>
>
>
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