I think this question has been answered in bits and pieces here and there, but I am still a bit unsure about what the best approach for this is: how to compare two coefficients from a multiple linear regression to see if the effect strengths are significantly different.
For example, I am interested in relating attitude (IV1) and behavioral control (IV2) to the medication adherence (DV). I found that standardized betas were 0.30 and 0.19 for attitude and behavioral control, respectively. Is it reasonable to say the attitude is the strongest predictor of medication adherence? If so, how can I test whether its effect is significantly different from those of the other predictors? I am using SPSS v19.