Instruction: Explain the principle of 'Common Cause' and its importance in the context of causal inference.
Context: This question tests the candidate's knowledge of the principle that suggests that if two variables are found to be correlated, there may exist a third variable that is a common cause of both.
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For instance, let's consider the scenario where we observe a correlation between ice cream sales and the number of drowning incidents. At first glance, one might be tempted to infer a direct causal relationship between these variables. However, upon applying the principle of 'Common Cause', we recognize that both ice cream sales and drowning incidents could be influenced by a third variable, which, in this case, is the temperature. Higher temperatures lead to an increase in ice cream sales as people seek to cool off, and simultaneously, more individuals are likely to engage in swimming activities, thus increasing the potential for drowning incidents. Here, the temperature acts as the common cause.
The importance...