Statistics 101

Cross-posted on Blue Mass Group, because Bill is on vacation.
The new study put out by the Boston Foundation gives a superb example of a principle from Statistics 101: correlation is not causation.
In other words, just because THIS happens and THAT happens, THIS did not necessary cause THAT.
Just because charter schools students on average spend more time in school and charter school students get better grades on tests ('though they don't, come to think of it), the time spent in school does not necessarily cause the better grades.
In order to prove that, you would have to control all other variables. You'd have to have exactly the same sort of kids--same grades, study habits, family involvement, neighborhoods, ethnicity, disabilities. You'd have to change ONLY the time spent in school: not, say, the amount of family involvement you have to have in a "choice" program.
This would, one would hope, be screamingly obvious to the reporter at a metropolitan daily, not to mention the backer of charter school research, but, alas, it appears their educations did not extend quite so far.

(And yes, Worcesterites, that is the same Paul Grogan who is keynoting the new Worcester Education Collaborative's inaugural event next week! Interesting choice, don't you think?)