Therefore, the probability of suicide among nongun owners = C/(C+D) = (10/100,000)/(1.50) ≈ 6.67 per 100,000 persons per year; and the probability of suicide among gun owners = (2.25)(C/C+D) = 15 per 100,000 persons per year.

The attributable risk is the difference between the probability of suicide among gun owners, and the probability of suicide among nongun owners: 15–6.67 ≈ 8.33 suicides per 100,000 attributable to gun ownership. The interpretation of this attributable risk depends on the actual causal mechanism linking exposure and outcome. In our example, there would be about 8.33 suicides per 100,000 that might be preventable by restricting access to guns, if guns were to play a causal role in the risk of suicide.



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