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Re: st: RE: Mean test in a Likert Scale

From   Maarten Buis <>
Subject   Re: st: RE: Mean test in a Likert Scale
Date   Mon, 3 Sep 2012 18:00:02 +0200

On Mon, Sep 3, 2012 at 4:54 PM, Yuval Arbel wrote:
> Nick and Maarten, Note, that Kmenta's message is to prefer models with
> less restrictions.

As always, there is no such thing as a free lunch. Less restrictions
typically cost statistical power, and if the restriction works well
for a particular applications, not using it will be a waste. Moreover,
such statements are in practice used to prefer models with less known
restrictions over models with well known restrictions. For example, I
have seen it used to prefer an -oprobit- over an -ologit- because
-ologit- implies the proportional odds assumption and -oprobit-
implies an equivalent assumption with a less memorable name.

> Moreover, are you suggesting we can deal in the same manner with
> quantitative values and ordinal variables? if our independent
> variables are  what subjects marked on a questionnaire on a scale
> between 1 to 5 is  the statistical treatment within a regression
> analysis framework should be identical to an independent variable
> measured in US dollars?

No, all I am saying is that I do not rule out that there exists an
application where treating a ordinal variable as having a linear
effect works well enough and that it is worth checking whether that is
the case, as you can safe a lot of power that way. Moreover, an amount
in dollars may not be as cardinal as one might hope; often respondents
round their answers considerably even if asked to provide exact

All I am saying is know your data, and make sensible rather than
dogmatic decisions. I guess there aren't many people who disagree with
that ;)

-- Maarten

Maarten L. Buis
Reichpietschufer 50
10785 Berlin
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