"In its coverage, the august New York Times sent a mixed message. Its first headline said "Teacher Quality Widely Diffused, Ratings Indicate,"
which implied that the ratings actually measured teacher quality and
meant something real and important. And indeed, the first three
paragraphs stated that every corner of the city, from the poorest to the
most affluent districts, had teachers who were the most and least
successful.
But the fourth paragraph of the Times story revealed the
statistical inadequacy of the measures: "... the margin of error is so
wide that the average confidence interval around each rating spanned 35
percentiles in math and 53 in English, the city said. Some teachers were
judged on as few as 10 students." With such a large margin of error,
it's hard to know how anyone could take these ratings seriously. The
precise numbers attached to each teacher's name are nothing more than
junk science."
aqui.
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