Average of gains of test group in excess of control -5.85 -3.36 Median of gains of test group in excess of control -7.75 1 P. E. of difference +-3.05 +-3.38 Average in terms of P. E. -1.92 -.87 Median in terms of P. E. -2.54 .26 The figures given above show no gain in the Healy test as a result of operation. Both after six months, and after twelve, we find that the test group has gained no more than the control group. As before there are individual cases showing considerable gain in the second period, but these are matched by control cases which reveal equal or even greater gains. In the test group, 5 cases lost in the second period in comparison with the first, 18 gained, and 7 gained as much in the second period as in the first. The control group lost in the second period in 5 cases, gained in 18, and gained as much as in the first period in 7 cases. The two groups, then, are practically equal, both showing a gain in the second period, but this gain cannot be due to the operations, since the control group did not undergo operation. TABLE XXII Healy A, Second Retests, 18 Pairs N[16] Test Group (A) Control Group (B) Test 1 Test 3 Gain Test 1 Test 3 Gain A-B 12 20 1 -19 -10 41.5 51.5 -70.5 23 49.5 62.5 13 4 64 60 -47 15 7 19 12 1 54.5 53.5 -41.5 1 -22 11 36 -50 11 61 -25 2 28.5 24.5 -4 3 19.5 16.5 -20.5 3 21.5 15.5 -6 17 25.5 8.5 -14.5 19 57.5 60.5 3 -22 -15 7 -4 13 43 62.5 19.5 -1.5 21.5 23 -3.5 21 20 38 18 70.5 88 17.5 .5 10 -12 11 23 27 48.5 21.5 1.5 14 12.5 77 64.5 -5 48.5 53.5 11 27 -25 25.5 50.5 2 39.5 37.5 13 11 -8 15.5 23.5 -29 -20 9 14.5 16 49 79 30 30 45.5 15.5 14.5 7 -6 16 22 45 11 6.5 15.5 28 29.5 77.5 48 64.5 83.5 19 29 18 -13.5 13.5 27 -32 -35 -3 30 20 0 55 55 30 48.5 18.5 36.5 Av. 13.81 36.92 23.11 5.77 32.25 26.47 -3.36 M 22.5 18.75 1 75%ile 33 44 14.5 25%ile 7.5 8.75 -22.25 Q 12.75 17.62 18.37 P. E. (distribution) 11.5 17.72 17.86 P. E. (average) +-2.7 +-4.22 +-3.88 Av.=-.87 P. E. M.=+.26 P. E.