Question

Name and describe the 3 criteria that must be met before a casual claim can be made. Then explain how/why quasi-experimental designs differ from experimental designs with respect to their ability to make casual claims.

Answer 1

The three criteria for causal association are:

- covariation: the causal variable has to vary systematically with the variable that it is thought to be caused.

- temporal precedence: the variable that is supposed to cause the effect should be present before the effect that it is known to have caused.

- elimination of extraneous variables: also, to establish causality, all the variables that are undesired have to be eliminated and then causality requires to be established.

In experimental studies, participants will be randomly assigned to either the control group or the experimental group whereas in a quasi experimental design the assignment of subjects in groups is not random. When there is causality, it could only be claimed in non random studies. This results in causal inference. Since, in quasi experimental designs, the assignment of variables is non random and it cannot be made certain that the measured or unobserved variables are kept controlled, the association is causal.