Wednesday, January 23, 2013

Survivor bias

There has been some discussion about meony from parents leading to a lower GPA from both Andrew Gelman and I.  One of the comments at Andrew Gelman's site got me thinking:

” The higher graduation rate of students whose parents paid their way is not surprising, she said, since many students leave college for financial reasons. (…)
Oddly, a lot of the parents who contributed the most money didn’t get the best returns on their investment (…) Their students were more likely to stay and graduate, but their G.P.A.’s were mediocre at best, and some I didn’t see study even once.”
What is the actual target of inference here?   Is it GPA or is it graduation? 

When I was in the corporate world I never was asked for my transcripts (my degree, all of the time but my transcripts never).  Having 2 years of college and then dropping out leads to worse life outcomes than having a degree, so far as I can tell. 

Or put it another way, what would you prefer:

  1. A child who got high marks but did not complete their program?
  2. A child who got low marks but earned a degree?
Insofar as university education is a credentaling and signaling system, the second piece would be far better. 

But even more interesting, the authors comments support my intuition precisely -- parental funding keeps marginal students in school.  From a causal perspective this is way more interesting than the headline effect of giving dropping grades and is way more intuitive as well. 

1 comment:

  1. Putting aside the more substantive issues for a moment, the discussion of the relative benefits of GPA versus graduation reminds me of an old joke:

    "What do you call a guy who graduates dead last in his class at med school?"

    "I give up. What do you call a guy who graduates dead last in his class at med school?"