http://spssx-discussion.165.s1.nabble.com/PCA-factor-score-uses-tp1072110p1072113.html
construction. By seeing which items load say |.40|, you can see if they
Fredric E. Rose, Ph.D. wrote:
>This was very helpful. To answer your question: Participants viewed images
>of couples that were/were not interracial and answered several questions.
>The first factor seemed related to a situational interpretation (e.g.,
>judgments about the couple's happiness, etc.) while the second was about
>more innate racist attitudes (willingness to have the couple over for
>dinner, etc).
>
>The questions were mixed in wording but we reversed scored several so that
>higher scores always meant more positive attitudes.
>
>I have two questions:
>
>1. How can I find out what "end" of the scale my groups are on? Just look
>at the group means of the scales? What is interesting is that the groups
>who viewed same-race couples (white-white or black-black) had the negative
>scores on factor 1, while the mixed race groups had positive scores. I'm
>curious to know if this means the same race groups reported LESS positive
>attitudes towards the couples than the mixed race groups.
>
>2. When you say " it is traditional to calculate scale scores by
>summing items, reflecting those items that have negative weights" what did
>you mean by reflecting those items that have negative weights? Reverse
>score items that load negatively on that factor?
>
>Thanks for your explanation. Most of the readings I have don't say anything
>more about factor scores other than they can be used in plots.
>
>Fred
>
>
>On 11/15/06 6:07 AM, "Art Kendall" <
[hidden email]> wrote:
>
>
>
>>You can use the factor scores in any design role.
>>Think of the factor scores as z-scores. Mean of zero, SD of 1.
>>
>>What interpretation did you give to the two factors? Are the factors
>>bipolar or unipolar?
>>
>>If you have 2 groups of respondents, and the mean factor scores you
>>mention are for these groups, then group 1 is at one end of the scale
>>and group 2 is at the other. The direction of factors is completely
>>arbitrary.
>>
>>When developing scales, it is traditional to calculate scale scores by
>>summing items, reflecting those items that have negative weights.
>>Since reliability, correlations etc. are not changed by dividing by a
>>constant, you might want to work with a mean of the items.
>>
>>It is also possible that you would want to reflect one or both scales so
>>that the high end is meaningful, e.g., high scores mean more racism.
>>The choice of direction is usually made to make correlations, etc., with
>>other variables have less complex verbal explanations.
>>
>>Art Kendall
>>Social Research Consultants
>>
>>
>>Fredric E. Rose wrote:
>>
>>
>>
>>>I'm not entirely familiar with PCA and could use some help.
>>>
>>>I've used PCA w/varimax rotation to reduce 10 variables (answers to a racism
>>>attitudes questionnaire) down to 2 factors. I want to know if the
>>>calculated factor scores for each participant can then be used as a
>>>dependent variable in subsequent analyses, or whether I should simply
>>>combine the variables loading on the respective factors and use those? My
>>>problem is in interpreting the factor scores: Group 1 has a mean of -2.72
>>>and Group 2 has a mean of 2.68. These are significantly different, but I'm
>>>not sure what the means represent (the raw data are scores ranging from 1 to
>>>10, so there are no negatives).
>>>
>>>Thanks for any insight.
>>>
>>>Fred Rose
>>>
>>>
>>>
>>>
>>>
>>>
>
>--
>Fredric E. Rose, Ph.D.
>Assistant Professor of Psychology
>Palomar College
>(760) 744-1150 x2344
>
[hidden email]
>
>
>
>