Date:         Wed, 2 May 2007 19:00:44 -0700
Reply-To:     David L Cassell <davidlcassell@MSN.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         David L Cassell <davidlcassell@MSN.COM>
Subject:      Re: rescaling categorical survey data
In-Reply-To:  <200705012054.l41KqlU3019088@malibu.cc.uga.edu>
Content-Type: text/plain; format=flowed

schant508@HOTMAIL.COM wrote:
>
>Does anyone know of the correct way to rescale categorical survey data? I
>have old data that is ranked from 1-4, but the new survey data (same
>questions) is scaled from 1-7. How do I correctly map the 1-4 values to
>the new 1-7 values?
>
>Thank you.

Peter is right.  There is no way to do this.

Even if there is no change in *anything* *whatsoever*, it may be that
1 maps to 1 and 4 maps to 7, or *not*.  Maybe 1 will have to map to 2
in the new scale.  This is often a subject-matter area, not a data-analyst
area.

But there is usually some change other than the scale.  Are the questions
*exactly* the same?  Are they being asked in *exactly* the same place in
the survey form?  Are the preceding questions still *exactly* the same?
Unfortunately, changes in these things can have important effects on
your instrument.  There's a whole field of study on this type of problem
in developing surveys.. and there are plenty of other people who study this,
learning how to make their surveys say whatever they want them to.

So mapping your 1-4 scale to a new 1-7 scale may be really hard.  And
errors on your part may have impacts on the comparisons you apparently need
to run...

HTH,
David
--
David L. Cassell
mathematical statistician
Design Pathways
3115 NW Norwood Pl.
Corvallis OR 97330

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