"Donald Burrill" <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> On Sat, 8 Sep 2001, Magenta wrote in part:
> > You would then be able to use, e.g. ANOVA, on your test results, which
> would be numeric in millimeters.
>
> Or other units of length -- sixteenth-inches, micro-furlongs, etc.
> But really, you don't need a ratio scale for ANOVA, you know.
> At most you need an interval scale, and even then "approximately"
> (that is, approximately interval) works very well much of the time.
I got involved in a"how do you analyse a Likert scale" discussion a couple
of years ago. It was recommended to me that analysis using measures of
central tendency, etc, was okay, as long as - for example - if I got a mean
of 4.2 I could state what that mean meant.
My biggest problem with Likert (and similar) scales is the assumption that
there is within-subject and between-subject consistency in responding to the
items. For example, if I moderately agree with an item, then I have to
select between "agree" and "strongly agree" on a typical 5-point scale.
Sometimes I may choose "agree" and other times I may choose "strongly
agree", but at all times my "true" response would be "moderately agree".
Another respondent may choose "agree" for the same strength of feeling on
all items. (This is just like people deciding on "reasonable doubt" if they
are on a jury. One person's level may be 98% confidence, another's may be
only 80%. It's the lack of consistency that is the problem.)
One way to try to remove this problem is to behaviourally anchor the
options. I have not often seen this method used.
This is the reason I prefer visual analog scales, then the person decides
what their strength of feeling is. And it makes it easier to be consistent
between questions.
cheers
Michelle
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