Based on your description, I do not think that "clustering" is the correct term. I think that you want to adjust for the effects of location and age. I suggest a general linear model. But, you state that the data is "longitudinal" implying that you have repeated measures. If that is the case, then you may have to do something like a general linear mixed model with random effects.   Providing a sample of the data may be helpful to provide more specific recommendations.   ... View more

Thanks for providing this resource! ... View more

Thank you for your reply. No, I don't have statistical evidence as to whether the 2 groups should have similar scores. However, the groups have similar demographic and clinical characteristics and the researchers seem to think the scores should be similar. I haven't done any statistical test to determine if this is the case (so far, I've only run the usual proc freq/univariate procedures). Here comes a basic question regarding the chi-square test.....Would I use the code below to determine if there's an association between the completeness variable and site (researchers), and if so, then what would I need to do?     proc freq data=check; tables complete_rate*site/chisq; /*the 2 researchers are at different sites/medical facilities*/ run;     ... View more