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A recent study found that people who exercise at least $4$ times a week are less likely to have a criminal record than those who do not exercise at all.
This fact could be explained by
Simple coincidence since exercising has nothing to do with crime involvement.
Some other type of common response or confounding variable.
A possible causal link between exercise and lack of a criminal record.
A flaw in the implementation of the experiment.
Nothing; since this was an observational study, no real linkage can be made between exercise and criminal activity.