Eleftherios Kellis (A-33) conducted an experiment on 18 pubertal males. He recorded the electromyographic (EMG) activity at nine different angular positions of the biceps femoris muscle. The EMG values are expressed as a percent (0–100 percent) of the maximal effort exerted with the muscle and represent an average in a range of flexion angles. The nine positions correspond to testing knee flexion angles of 1–10, 11–20, 21–30, 31–40, 41–50, 51–60, 61–70, 71–80, and 81–90. The results are displayed in the following table. For subject 1, for example, the value of 30.96 percent represents the average maximal percent of effort in angular positions from 1 to 10 degrees Subject 1–10 11–20 21–30 31–40 41–50 51–60 61–70 71–80 81–90
1 30.96 11.32 4.34 5.99 8.43 10.50 4.49 10.93 33.26 2 3.61 1.47 3.50 10.25 3.30 3.62 10.14 11.05 8.78 3 8.46 2.94 1.83 5.80 11.59 15.17 13.04 10.57 8.22 4 0.69 1.06 1.39 1.08 0.96 2.52 2.90 3.27 5.52 5 4.40 3.02 3.74 3.83 3.73 10.16 9.31 12.70 11.45 6 4.59 9.80 10.71 11.64 9.78 6.91 8.53 8.30 11.75 7 3.31 3.31 4.12 12.56 4.60 1.88 2.42 2.46 2.19 8 1.98 6.49 2.61 3.28 10.29 7.56 16.68 14.52 13.49 9 10.43 4.96 12.37 24.32 17.16 34.71 35.30 37.03 45.65 10 20.91 20.72 12.70 15.06 12.03 11.31 28.47 26.81 25.08 11 5.59 3.13 2.83 4.31 6.37 13.95 13.48 11.15 30.97 12 8.67 4.32 2.29 6.20 13.01 19.30 9.33 12.30 12.20 13 2.11 1.59 2.40 2.56 2.83 2.55 5.84 5.23 8.84 14 3.82 5.04 6.81 10.74 10.10 13.14 19.39 13.31 12.02 15 39.51 62.34 70.46 20.48 17.38 54.04 25.76 50.32 46.84 16 3.31 4.95 12.49 9.18 14.00 16.17 25.75 11.82 13.17 17 11.42 7.53 4.65 4.70 7.57 9.86 5.30 4.47 3.99 18 2.97 2.18 2.36 4.61 7.83 17.49 42.55 61.84 39.70 Source: Data provided courtesy of Eleftherios Kellis, Ph.D.
Can we conclude on the basis of these data that the average EMG values differ among the nine angular locations? Let a ¼ :05.