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st: RE: Mean test in a Likert Scale

From   "David Radwin" <>
To   <>
Subject   st: RE: Mean test in a Likert Scale
Date   Thu, 30 Aug 2012 16:13:22 -0700 (PDT)


No, you can't correctly calculate the mean of an ordinal-level measure
like the Likert scale you describe, although plenty of people do it

But you can use -ttest- with these data if you first collapse each
variable to a dichotomous (dummy) variable, because the mean of a
dichotomous variable is identical to the proportion where the value is 1.
As a guess, you might set the highest two values to 1, the lowest two
values to 0, and the middle value to missing to calculate the proportion
agreeing or somewhat agreeing.

David Radwin
Senior Research Associate
MPR Associates, Inc.
2150 Shattuck Ave., Suite 800
Berkeley, CA 94704
Phone: 510-849-4942
Fax: 510-849-0794

> -----Original Message-----
> From: [mailto:owner-
>] On Behalf Of Leonor Saravia
> Sent: Thursday, August 30, 2012 3:23 PM
> To:
> Subject: st: Mean test in a Likert Scale
> Hello,
> I'm working with a survey that presents 26 questions and each of them
> has as possible answer a 5 point Likert scale from Desagree (1) to
> Agree (5). This survey was applyed for a treatment and a control
> group.
> As far as I know, it is possible to analyze the information given only
> by the proportions of each answer; for instance, 25% agrees, 50%
> desagree, or so.
> I have two questions that maybe one of you have had before:
> a) Is it possible to calculate the mean score of a sample (treatment
> or control group) - adding the individual answers - when one is
> working with a Likert scale?
> b) If it is possible to calculate a mean score of a sample when using
> a Likert scale, to compare the answers of the treatment versus the
> control group, is it well done if I use the 'ttest' command?
> Thank you in advance.
> Best regards,
> Leonor
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