On Fri, 28 Dec 2001, Petrus Nel wrote:
> I require some advice regarding the following: One set of variables is
> the grades obtained by students for different high school subjects
> (i.e. the symbols candidates obtained such as A, B, C, D, etc. for each
> subject). The other set of variables are the scores obtained for a
> college level subject (i.e. no symbols, just their percentages
> obtained). I want to determine the correlation between their grades
> for different high school subjects (A, B, C, D, etc.) and their
> percentage scores for a college level subject.
Why do you want to? _Nobody_ just wants correlation coefficients:
there's always something more that is desired.
> The grades obtained for their high school subjects were coded on the
> questionnaire as follows - 1=3DA, 2=3DB, 3=3DC, 4=3DD, 5=3DE, 6=3DF.
> I`ve entered the data for the grades as 1,2,3, etc. to indicate the
> grade (category) and the percentages (as the other variable) into SPSS.
> How do I proceed?
What follows assumes that the answer to "Why?" implies that correlation
coefficients are part of the desiderata, for good reason(s).
First, recompute each HS subject grade: e.g.,
NEWGRADE = 7 - OLDGRADE
so that both grades and percentages are coded in the same direction
(higher values = better performance); else your correlation coefficients
will be negative where the relationship is positive, etc.
Second, produce scatterplots of grade vs. percentage, grade vs. grade,
and percentqage vs. percentage, for all pairs whose correlations are of
interest: so that you can properly interpret correlation coefficients
when you get them (and can be prepared to deal with nonlinear
relationships, should there be any obvious from the plots).
For this purpose one needn't be too fancy: character plots will do,
high-resolution plots won't tell you anything more unless there are some
rather odd nonlinearities among the relationships.
Third, invoke SPSS's CORREL routine to calculate all pairwise zero-order
correlation coefficients.
Fourth, proceed with whatever your answer to "Why?" implies about
subsequent analyses and interpretation.
-- DFB.
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Donald F. Burrill [EMAIL PROTECTED]
184 Nashua Road, Bedford, NH 03110 603-471-7128
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