Junk science 101

[unixronin]

Yes, it’s more junk science out of the UPenn School of Medicine.  We’ve become accustomed to seeing some horrendously bad junk science out of the medical academic sector where firearms are concerned, but this is worse than most.  I honestly think this one is, methodologically speaking, possibly even worse than the Kellermann study.

News release here, American Journal of Public Health abstract here.

Let’s briefly summarize the methodology here.

First, Dr. Branas compiled a list of 677 people shot in the course of assaults in Philadelphia between 2003 and 2006, and determined that 6% of them were reported to have been in possession of a gun in a holster, pocket, waistband or vehicle when they were shot.  (Note:  By elementary arithmetic, that means 94% of those shot were unarmed.)

Next, Dr. Branas and his intrepid law students picked up the phone book, randomly called 684 people in Philadelphia who had not been assaulted, soon after reported shootings, and asked them whether at the time of the shooting they had a gun in their possession.

From these two sets of data, Dr. Branas somehow derived the conclusion that possessing a gun makes you 4.5 times more likely to be shot in an assault.

... No, I don’t see a logical path from data to conclusion either.  But I have a pretty good idea the conclusion was predecided and the study designed to fit it.

So!  Just for fun, let’s play a game.  Let’s see if we can think of ALL of the logical and methodological problems with this study.

Have at it!

Comments

One more thing...

[theonetruejim.livejournal.com]

They actually had a built-in control group (assuming they were careful enough to get the police reports for the assaults that made up the selection criteria for their study group - an assumption that is by no means certain). That would be the other parties in the assault. Unless the gunshots were self-inflicted, there was at least one other person in every case who was in possession of a firearm at the time of the assault.

Now, there's not enough data to be sure about any conclusions, but that didn't stop the original reporters, so I'll make up some data and form my own conclusion. I'm going to assume there was one and only one other person in each assault, none of the wounds were self-inflicted, and only a single party in each assault was actually shot.

With my "data" (which is probably more reliable than the study's control group), there were 677 people in possession of a firearm at the time of an assault resulting in a shooting that did not get shot. In contrast, there were 38-44 people in the study group who both were in possession of a firearm and got shot, in contrast to the 633-639 who were unarmed and got shot.

Based on the study methodology, I'd have to conclude you're about 16-19 times as likely to be shot in an assault if you're unarmed.

Re: One more thing...

[unixronin.livejournal.com]

Good point. :)