To conclude that the relationship between two variables is causal, there must be an association between the two variables. The presumed cause has to precede the presumed effect, and when a control variable is introduced the original association has to disappear.

Question

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For a relationship between two variables to be considered causal, the association must not disappear when a control variable is introduced; instead, the association should remain significant even after controlling for other potential confounding variables. The disappearance of the association upon controlling for another variable might suggest that the original association was due to the confounding variable, not a causal relationship.

To Conclude That the Relationship Between Two Variables Is Causal