title 'Reading rate and comprehension';
*-- 3 teachers each taught two classes, one using a 'contract'
    method, the other using a 'non-contract' method.
    The response variables are the reading rate and comprehension
    subtests on the Iowa Test of Basic Skills;
data readcomp;
   input teacher class $ rate comp;
cards;
 1 C 10 31
 1 C 12 22
 1 C  9 19
 1 C 10 21
 1 C 14 23
 1 N  9 14
 1 N  8 15
 1 N 11 16
 1 N  9 17
 1 N  9 17
 2 C 11 23
 2 C 14 27
 2 C 13 24
 2 C 15 26
 2 C 14 24
 2 N 11 15
 2 N 12 18
 2 N 10 16
 2 N  9 17
 2 N  9 18
 3 C  8 17
 3 C  7 15
 3 C 10 18
 3 C  8 17
 3 C  7 19
 3 N  9 22
 3 N  8 18
 3 N 10 17
 3 N  9 19
 3 N  8 19
;