I'm looking for the best way to report my simple mediation analysis using the PROCESS Macro on SPSS.
Hayes (2009) Introduction to Mediation and Moderation does not recommend reporting standardised coefficients, but in my undergraduate experience we have always reported the standardised coefficients. I'm wondering is there a place in my report (using APA guidelines) where I can justify why I've reported unstandardised coefficients rather than the standardised values. Also, within this model, looking at two unstandardised regression coefficients, does the larger one imply the relationship is stronger? I know this is true when comparing standardised coefficients but think it may be inaccurate to do with unstandardised coefficients.
Lastly, APA recommends the reporting of effect sizes. Is there an effect size that I can report in my model? I was going to report R-squared but absence of a direct or total effect makes this statistic unsuitable. Hayes (2009) book also does not advise reporting effect sizes. If I don't report an effect size how do interpret the strength of my associations?
Thanks in advance,
A confused final year psychology student
Best Answer
Q1: Concerning "...looking at two unstandardised regression coefficients, does the larger one imply the relationship is stronger?" No, it does not.
Q2: For effect size calculation for psychology and ANOVA read this, which gives one method of calculating effect size and says (follow the link for details):
Effect size, in a nutshell, is a value which allows you to see how much your independent variable (IV) has affected the dependent variable (DV) in an experimental study. In other words, it looks at how much variance in your DV was a result of the IV. You can only calculate an effect size after conducting an appropriate statistical test for significance.
However, note that in general that there are 50 to 100 different methods of calculating effect size. So that there are lots of choices for measures of effect size calculations.