Hi. I intend to do a meta-analysis on critical thinking. I have some questions concerning the variables of the study. Should critical thinking be the the independent variable of the study or the depedent variable? Or it can be both? Could we have one independent variables, that is, critical thinking, and a number of dependent variables in the study? For examples, could we explore the effect of critical thinking on the the four language skills (reading, writing, speaking, listening)? The answers are highly welcome. Thanks in advance.