In a study, an outcome variable has three categories. There are several factors in the study. We are determining how these factors influence the outcome variable.We have fitted multiple logistic regression and calculated relative risk ratio to determine whether a factor is significant risk factor for the outcome variable.
If there were only one country in this study, the statistical analysis so far described were enough. But, the problem is we have several countries, we are doing the same statistical analysis to determine which factors are significant for the outcome variable.
Now, we want to compare among the countries. How can we compare among the countries? Is there any statistical measurement by which we can compare among countries. Could you please share any reference where several countries were being compared?