# [Rasch] Rasch analysis of interval data

Thomas Salzberger Thomas.Salzberger at wu-wien.ac.at
Wed Jul 16 21:31:37 EST 2008

```At 13:19 16.07.2008, Anthony James wrote:

>Hi all,
>
>Has anyone ever tried to Rasch analyse a
>variable for which there¢s concatenation-based
>objective measurement? Suppose we make a height
>scale with 6 points:<?xml:namespace prefix = o
>ns = "urn:schemas-microsoft-com:office:office" />
>
>Very short (1), short (2), average height (3),
>quite tall (4), rather all (5), Very Tall (6)
>
>We measure some people with this scale and then
>Rasch analyses it and obtain Rasch height
>measures. How do these measures compare with
>persons¢ heights in centimeters or inches? Does
>the Rasch measure difference between a person
>who is 170 cm and a person who is 175cm equal to
>the Rasch measure difference between a person
>who is 180cm and one who is 185cm?
>
>I¢d love to see what happens. Pairing persons¢
>heights in cm and their Rasch heights
>simultaneously on a vertical line and comparing
>the calibrations give a good test of Rasch¢s interval scaling, I guess.
>
>Cheers
>
>Anthony

Anthony,

very interesting question. I am sure someone has
done this before. So I am also curious. Have you searched RMT?

However, I would not be totally surprised if
there be a deviance. Objective measurement of
length is one thing but if we ask human beings to
judge a person's height we might capture
something like "perceived height" rather than
"objective height". There could be a non-linear
relationship between objective height and
perceived height. So, Rasch could very well
provide a linear measure of the latent variable
but that variable could stand in a non-linear
relationship to objective length. Just a thought.

Best wishes
Thomas

_______________________________________________________
Dr. Thomas Salzberger
Österreichische Gesellschaft für Absatzwirtschaft
c/o Department of Marketing, Institute for Marketing Management
Augasse 2-6 / A-1090 Wien / Austria, Europe
Email: Thomas.Salzberger at wu-wien.ac.at
Tel: (+43-1-) 31336 4406
Personal Fax: (+43-1-) 31336 90 4406
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