No sooner do I complain that the dead trees don't value statistical inference than I come across this from Rob Capriccioso:
Poor Mrs Graneggen. She apparently really screwed me up. Because, although she was my favorite grade school teacher - and I feel like I learned a lot from her - she happened to have a vagina. And a new study indicates that I, the strapping lad that I am, should have learned more from my teachers with penises.
Or at least that's one ridiculous premise that could be deduced as a result of new research from Thomas Dee.
It certainly could be deduced - but only if you were a cretin.
Dee's strongest finding - in this paper (pdf) summarized here (pdf) - is that in sciences (but not in English or social studies) boys test "scores drop by 5% of a standard deviation if they have a female teacher [rather than a male one]."
Now, 5% of a standard deviation is not much in absolute terms, although it is, as Dee says, a fair chunk of the gender gap in scores. So Rob's trite claim that "gender is only one aspect of an educational experience" is wholly consistent with the finding.
What's more, there's uncertainty around this estimate; the standard error is 2.8% of a standard deviation in the test score. This implies that, even within the sample of boys Dee studied, roughly one in 25 would benefit from a female teacher.
I reckon Rob is committing (or nearly committing - that "could" hedges bets) two errors common to journalism.
1. The preference for striking human interest anecdotes over statistical tendencies; "Mrs Graneggan was a great teacher, so don't worry about evidence about average teachers".
2. Mistaking tendencies for absolutes. The strongest that Dee is claiming is that, on average, boys do fractionally better (in science) with (average) male teachers than with (average) female ones. This is wholly consistent with many boys doing better with average female teachers, and many more doing even better with good ones. The data's very noisy. Just because a correlation is positive, does not mean it is equal to one. Mrs Grannegan doesn't seem to have taught Rob that.
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