Re: st: comparing coefficients accross models

 From Maarten buis <[email protected]> To [email protected] Subject Re: st: comparing coefficients accross models Date Thu, 11 Jan 2007 07:13:40 +0000 (GMT)

```--- Traci Schlesinger <[email protected]> wrote:
> By saying I should 'fudge it and compare them indirectly' do you
> simply mean that i should compare them 'by eye' -- stating that not
> only is the coefficient for mt_b larger in the model for blacks but
> that the t-score is also higher?   This is not so terrible for this
> data, since according to the Bureau of Justice Statistics, this is
> the full population of people admitted to prison (not a sample), but
> I still think many people (esp. reviewers) would not be convinced

If you have the population, then "comparing them by eye" is all you can
do (or go Bayesian, but you probably don't want to go there).
Frequentist testing assumes that all uncertainty about a parameter is
the result of the fact that we only observed a random sample from the
population, not the actual population itself. Then it imagines what the
population would be like if the null hypothesis were true. Then it
looks at how likely it is to draw a random sample with the observed
test statistic or extremere, the p-value. If it is very unlikely to
draw such a sample "by accident" then we think that there must be
something wrong with the null hypothesis. Since you don't have a
sample, but the population concepts like the p-values loose their
meaning.

The idea behind testing is that what you find in a sample gives you
information about what happens in the population, but that information
is uncertain due to the fact that you are only looking at a sample.
Testing quantifies the uncertainty due to sampling. You have no
uncertainty on that account. You may have other sources of uncertainty:
is my model correct, are my variables measured without error, etc. But

-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------

___________________________________________________________
What kind of emailer are you? Find out today - get a free analysis of your email personality. Take the quiz at the Yahoo! Mail Championship.
http://uk.rd.yahoo.com/evt=44106/*http://mail.yahoo.net/uk
*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/
```