Wednesday, July 2, 2008

Causation or Correlation?

The Volokh Conspiracy has a fascinating comment on gun-control studies in the medical literature.

Apparently yet another of these "causation or correlation" studies has been released. The authors claim that keeping a gun in the house increases the risk of suicide and homicide. Although these authors flat-out admit that they do not have any data on whether the fatal firearm is the same one that was kept in the victim's home (Kellermann NEJM '93 tried to deflect questions on that subject), even though they (like Kellermann) interviewed the family members.

One of the commenters, "30yearProf", had this to say.


QUOTE: Second, the gun in the home may not have been the gun used in the death.

Incredible! They interviewed the family members! They could have easily found this out by asking the very people they interviewed (who would know). After all, the implication sought from ALL these pseudo-scientific "studies" is that YOUR gun will hurt YOU. Here, they had the chance to ask whether or not it was YOUR gun that "caused" YOUR death and they failed to ask. Logically, that raises a strong suspicion that they did not ask because the researchers either knew or strongly suspected that the answer would not support their desired result.
Clever boy! What an interesting observation.

Correction: It seems that these researchers didn't actually interview any of the victims' families. Instead, they used eleven-year-old data from a CDC study, so they know even less about the victims' risk factors: arrest records, alcohol abuse, illicit drug use, violence, etc. At least Kellermann did conduct proxy interviews, but he failed to ask the crucial question: "Was the victim shot with his own gun?" And the comment by "30yearProf" applies to Kellermann's 1993 study (and probably others, too.). The present study, by Dahlberg et al, is even more deficient than that. And, of course, confuses causation and correlation. That hasn't changed.

No comments: