On 1 Jun 2000 20:26:18 -0700, [EMAIL PROTECTED] (Lance Hoffmeyer) wrote:
> I have collected data using a questionaire with 20 rating scales. The
> respondents were asked to use tick marks to rate the answers so there were
> no anchors. Some people have minimums of '0' and maximums of '10' while
> others have minimums of '6' and maximums of '68'. I wish to do a factor
> analysis so I need to get everything on the same scale. Initially, I thought
> of row standardizing the data. After thinking about it I am not completely
> certain this solves the scale problem.
- Well, you are not going to solve "the scale problem" by merely
subtracting out the mean. You have eliminated all possibility of
looking at between-subject differences in the over-all Means, by not
providing anchors; and you can't look at single ranges, either.
"Magnitude estimation" would have eliminated zero and then used logs
of the scores; that would have preserved a semblance of "range" for
each subject, though it still tosses out the mean.
> ... My first question is whether row
> standardization puts all respondents data onto the same scale? The second
> question is what would be another technique or a better technique to get all
> data onto the same scale?
>From where you are, you can: Standardize by mean-and-SD, or take
ranks, or (further) convert the ranks to normal-deviates. Whichever
of these you do, the main criticism you receive should be about your
data collection which left these options.
The far better technique is to ponder and figure out your
scaling/scoring questions before you collect the data.
What did you hope to gain by not providing anchors?
--
Rich Ulrich, [EMAIL PROTECTED]
http://www.pitt.edu/~wpilib/index.html
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