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Hi all,
Can I check my understanding of a procedure? I want to remove the influence of 4 demographic variables (gender, age, degree level, and local vs. international student status) from a set of teaching evaluation scales, before performing subsequent analyses. Can this be done in SPSS by entering these variables as predictors of each scale in a multiple regression, and saving the residuals? If so, is any particular kind of residual to be preferred (e.g. unstandardised, standardised, Studentized, etc.)? Thanks in advance, Paul |
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Stephen Brand Paul, You can do this, with some caveats. The procedure you describe removes the influence of demographic characteristics from the teacher evaluation ratings, but if you are going to relate the residuals to other variables (e.g., years of experience), you should consider whether or not you want to remove the influence of these variables from these other variables. You do not have to - it all depends on your question - it is something you should consider. This may be stating the obvious, but you should deal with degree level by dummy coding levels, rather than entering it as a single variable. As you note, SPSS will allow you to save residual scores from the regression equation. Studentized residuals are useful for identifying outliers in the data, but are not what you want for simply computing residualized scores. Whether you use unstandardized or standardized residuals depends on whether or not you want to interpret the residual scores in a norm-referenced form. HTH, Stephen Brand For personalized and professional consultation in statistics and research design, visit www.statisticsdoc.com -----Original Message----- From: SPSSX(r) Discussion [mailto:[hidden email]]On Behalf Of Paul Ginns Sent: Monday, December 11, 2006 10:40 PM To: [hidden email] Subject: partialling out the influence of demographic variables Hi all, Can I check my understanding of a procedure? I want to remove the influence of 4 demographic variables (gender, age, degree level, and local vs. international student status) from a set of teaching evaluation scales, before performing subsequent analyses. Can this be done in SPSS by entering these variables as predictors of each scale in a multiple regression, and saving the residuals? If so, is any particular kind of residual to be preferred (e.g. unstandardised, standardised, Studentized, etc.)? Thanks in advance, Paul |
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In reply to this post by Paul Ginns
Dear All
Does anyone know about a syntax or a macro to apply Olsen's correction, as described in the following reference? Unlike Heckman's procedure, Olsen's does not assume bivariate normality, which makes his proposal more general. Randall J. Olsen, "A Least Squares Correction for Selectivity Bias", Econometrica, Vol. 48, No. 7. (Nov., 1980), pp. 1815-1820. Many thanks Cheers E. |
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