Also I'd look at the frequencies for both samples. Odd scales tend to show larger hits for the middle point--which 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
Sent: Tuesday, May 26, 2009 3:05 PM
Subject: Re: converting 1-5 rating into 1-6 rating scale
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 z-score for each case. The following formula does the trick for converting a 5-pt scale to a 6-pt scale. Scale end-points are maintained and the converted z-scores will match the original z-scores.
COMPUTE NEWSCORE = (OLDSCORE-3)*(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 z-scores 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
Next, run descriptives of the saved z-score variables to check the high and low z-scores, which should be the same for the original and the converted scales.
DESCRIPTIVES VARIABLES = ZOLDSCORE ZNEWSCORE
--- On Tue, 5/26/09, ajay atluri <email@example.com> wrote:
From: ajay atluri <firstname.lastname@example.org>
Subject: converting 1-5 rating into 1-6 rating scale
Date: Tuesday, May 26, 2009, 12:39 PM
I am working on SPSS 16 Base. I have 500 participants and 70
questions in the data. All these questions are of 1-5 point scale in
2007 data. But, 2009 data we have same set of participants and
questions but rating was changed from 1-5 scale rating to 1-6 rating
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 5-5, 4-5 and 3-5 by considering the following
percentage of respondents 25%, 70% and 15% into 5. This list will go
Does any one in the forum has done in a similar way? If so, please
share the syntax with me.
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