[michaelt]

  from the outside, it had really high pass rates, too.
  [...] Many (including me) dropped the course,

The survey in the article actually divides students into four groups for this reason. They count those dropping the course; those not attending the exam; those attending the exam and failing; and those attending the exam and passing.

[ThePadawan]

Which is also why I'm not sure that picking CS1 was a good choice for study.

Surely failing CS1 is highly correlated with dropping out of a CS degree completely - or rather, it would be interesting to see if indeed failing CS1 was anticorrelated with failing other first-year CS courses.