Thursday, November 13, 2008

Subtle and incorrect assumption about statistics of heart transplants

A Yahoo news story reports results of a study showing that people receiving heart transplants do better when the transplant comes from the same gender. The subtle statistical assumption comes from this line -
"Three-fourths of heart transplants are done in men, so by necessity, many must receive organs from the opposite sex."
So, as we might suspect, more men need heart transplants than women. I would guess that the phrase "by necessity" is based on the assumption that donor hearts are available 50/50 guys and gals. Why should that be the case? If hearts for transplant become available due to unfortunate accidents associated with car accidents, motorcycle accidents without helmets, etc. aren't such things more associated with males than females? Thus I would expect more male hearts are available than female. In fact the report says that:
"Among the recipients 77 percent of the men and 51 percent of the women were of the same gender as their donors."
Which already supports my supposition that more male hearts are available for transplants than female. Sometimes innocuous seeming statements in these news stories have some unwarranted assumptions.

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