Sometimes clarity comes sloooowly!
From Marginal Revolution:
Did Bill Gates waste a billion dollars because he failed to understand the formula for the standard deviation of the mean? Howard Wainer makes the case in the entertaining Picturing the Uncertain World (first chapter with the Gates story free here). The Gates Foundation certainly spent a lot of money, along with many others, pushing for smaller schools and a lot of the push came because people jumped to the wrong conclusion when they discovered that the smallest schools were consistently among the best performing schools.
Here’s some data from North Carolina that seems to suggest small schools outperform large schools:
Again, Alex Tabarrok at Marginal Revolution:
Seeing this data many people concluded that small schools were better and so they began to push to build smaller schools and break up larger schools. Can you see the problem?
The problem is that because small school don’t have a lot of students, scores are much more variable. If for random reasons a few geniuses happen to enroll one year in a small school scores jump up and if a few extra dullards enroll the next year scores fall.
Read the whole thing!
Then go read, well, a good book, like Picturing the Uncertain World, or even this classic.
Down the linky path: Instapundit, Megan McArdle, Marginal Revolution, Amazon, Princeton Press