Also I'd look at the frequencies for both samples. Odd scales tend to show larger hits for the middle pointwhich is frequently a proxy answer for "I don't know" or "I don't care". Even scales force the respondent to a make a positive or negative choice.
 Original Message 
From: King Douglas
To: SPSSXL@LISTSERV.UGA.EDU
Sent: Tuesday, May 26, 2009 3:05 PM
Subject: Re: converting 15 rating into 16 rating scale
Ajay,
Is there any reason you need the new values to be integers? If you are going to aggregate the data and report means, then the converted scale should maintain the zscore for each case. The following formula does the trick for converting a 5pt scale to a 6pt scale. Scale endpoints are maintained and the converted zscores will match the original zscores.
COMPUTE NEWSCORE = (OLDSCORE3)*(5/4) + 3.5.
What the preceding does is subtract from each original score the original scale midpoint, then multiplies the result by (the range of the new scale divided by the range of the old scale), then adds to that result the midpoint of the new scale.
To check the accuracy of the conversions, run descriptives of old and new variables. Include the subcommand /SAVE in order save the zscores of both the original and the converted scores. Any score that is an endpoint on the original scale should be an endpoint on the new scale.
DESCRIPTIVES VARIABLES = OLDSCORE NEWSCORE
/SAVE
/SORT.
Next, run descriptives of the saved zscore variables to check the high and low zscores, which should be the same for the original and the converted scales.
DESCRIPTIVES VARIABLES = ZOLDSCORE ZNEWSCORE
/SORT.
 On Tue, 5/26/09, ajay atluri <atluriak@gmail.com> wrote:
From: ajay atluri <atluriak@gmail.com>
Subject: converting 15 rating into 16 rating scale
To: SPSSXL@LISTSERV.UGA.EDU
Date: Tuesday, May 26, 2009, 12:39 PM
Hi Team,
I am working on SPSS 16 Base. I have 500 participants and 70
questions in the data. All these questions are of 15 point scale in
2007 data. But, 2009 data we have same set of participants and
questions but rating was changed from 15 scale rating to 16 rating
scale.
At this juncture, I would like to convert all 2007 data into 6 point
scale. To do this i have defined some formulae.
We need to convert 75% who has given the answer as 5 and 12% who have
given the answer as 4 into 6. And for getting number of responses for
5, I will be converting 55, 45 and 35 by considering the following
percentage of respondents 25%, 70% and 15% into 5. This list will go
on.
Does any one in the forum has done in a similar way? If so, please
share the syntax with me.
Thanks,
Atluri
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