Using Abortion Debates to Explain Bayesian Statistics

(cc from Wikipedia)
(cc from Wikipedia)

I’m never one to pass up a chance to leverage people’s interest in a hot-button social issue to talk about probability theory.  I’m over at Ethika Politika today, talking about how base-rate neglect can skew people’s understanding of the significance of screening test (specifically, those for fetal abnormalities)

A New Danger to Expecting Mothers: Statistical Illiteracy

Abortion, the talking point goes, is a private matter between a woman and her doctor.  But, after a series of missteps by companies offering early genetic screening, pro-choicers might want to append “… and a mathematician” to that phrase.

[…]

Usually, when advertisers tout a statistic of 99 percent accuracy, they’re talking about a true positive rate.  That is: If you do have a genetic abnormality, the test will say that you do 99 percent of the time.

The trouble is, although a high true positive rate is nice, it’s not sufficient to make a test useful.  At the extremes, I could run a very shady fetal screening company that had a 100 percent true positive (“accuracy”) rate, if I wasn’t above a bit of flim-flam.

All I’d have to do is take a blood sample from each woman who came to my clinic, wait a few days after her appointment, and then gravely call her to say that the results had come back positive—without ever having screened her blood at all!  I’d be guaranteed to have a 100 percent true positive rate, because I would just tell every woman that her fetus was abnormal, meaning that I’d end up telling the truth to every woman whose pregnancy was actually unusual.

That would be cold comfort to all the women with run-of-the-mill pregnancies whom I’d misled.

Read more at Ethika Politika…

 

And, if you’re looking for MLK-blogging, today, check out my radio show this week, which is focused on Martin Luther King Jr’s martyrion (witness) and the Christological significance of the way he made the invisible violence of his communities visible, by offering his own body as place it would be recorded.

"Well, I would love to know if you now believe that homosexuality is intrinsically disordered."

Go Ahead, Tell Me What’s Wrong ..."
"Any chance of you ever addressing the evidence that led you to accept the truth ..."

Letting Go of the Goal of ..."
""Wow, an unevidenced assertion from a religious dipshite. "Your quotes are the evidence and reason ..."

This is my last post for ..."
""Congrats on leaving your brain behind!"Comments like yours are why lots of atheists leave atheism. ..."

This is my last post for ..."

Browse Our Archives

Follow Us!


What Are Your Thoughts?leave a comment