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Re: st: Nominal or ordinal?


From   Steve Samuels <sjsamuels@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Nominal or ordinal?
Date   Thu, 12 Aug 2010 21:30:36 -0400

Chelsea,  Ordinal logistic regression does require an assumption that
categories are "equally spaced".  Perhaps you are confusing ordinal
logistic regression with multiple regression on the category scores.

Steve

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Steven Samuels
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On Thu, Aug 12, 2010 at 8:38 PM, Clive Nicholas
<clivelists@googlemail.com> wrote:
> Chelsea B Polis wrote:
>
>> I am working with a dependent variable that has the following four potential responses: (1) Not Likely, (2) Slightly Likely, (3) Quite Likely, (4) Extremely Likely.
>>
>> A colleague thinks this is an ordinal variable which should be analyzed using ordered
>> logit regression.  My sense was that this is a nominal variable, and should be analyzed > using multinomial regression - since we cannot know if the levels are
>> equally spaced in people's minds.
>
> In addition to the excellent responses given, with which I concur, you
> could treat the variable as multinomial, regress it onto your
> independent variables by fitting -mlogit-, and then test the IIA
> assumption with the user-written -mlogtest- (downloadable via STB:
> -net stb 58 sg155-). If the IIA is violated, then you might consider
> combining a couple of the indicators of your response variable before
> running it through -ologit- or -oprobit-. Then again, you might think
> of all this as rather too exotic.
>
> --
> Clive Nicholas
>
> [Please DO NOT mail me personally here, but at
> <clivenicholas@hotmail.com>. Please respond to contributions I make in
> a list thread here. Thanks!]
>
> "My colleagues in the social sciences talk a great deal about
> methodology. I prefer to call it style." -- Freeman J. Dyson.
>
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