The F distributions are skewed to the right.
The F distributions are a family of distributions with two paramenters, the degrees of freedom of the sample variances in the numerator and denominator of the F statistic. The numerator degrees of freedom are always given first. The F distributions are not symmetric but are right skewed. The density curve figure illustrates the shape. Because sample variances cannot be negative, the F statistic takes only positive values and the F distribution has no probability below zero. The peak of the F density curve is near one; values far from one in either direction provide evidence against the hypothesis of equal standard deviations.
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 15 | ||
1 | .05 .01 | 161 4052 | 200 4999 | 216 5403 | 225 5625 | 230 5764 | 234 5859 | 237 5928 | 239 5981 | 241 6022 | 242 6056 | 243 6082 | 244 6106 | 246 6157 |
2 | .05 .01 | 18.51 98.49 | 19.00 99.01 | 19.16 99.17 | 19.25 99.25 | 19.39 99.30 | 19.33 99.33 | 19.36 99.34 | 19.37 99.36 | 19.38 99.38 | 19.39 99.40 | 19.4 99.4 | 19.4 99.4 | 19.4 99.4 |
3 | .05 .01 | 10.13 34.12 | 9.55 30.81 | 9.28 29.46 | 9.12 28.71 | 9.01 28.24 | 8.94 27.91 | 8.88 27.67 | 8.84 27.49 | 8.81 27.34 | 8.78 27.23 | 8.76 27.13 | 8.74 27.05 | 8.70 26.87 |
4 | .05 .01 | 7.71 21.20 | 6.94 18.00 | 6.59 16.69 | 6.39 15.98 | 6.26 15.52 | 6.16 15.21 | 6.09 14.98 | 6.04 14.80 | 6.00 14.66 | 5.96 14.54 | 5.93 14.95 | 5.91 14.37 | 5.86 14.2 |
5 | .05 .01 | 6.61 16.26 | 5.79 13.27 | 5.41 12.06 | 5.19 11.39 | 5.05 10.97 | 4.95 10.67 | 4.88 10.45 | 4.82 10.27 | 4.78 10.15 | 4.74 10.05 | 4.70 9.96 | 4.68 9.89 | 4.62 9.72 |
6 | .05 .01 | 5.99 13.74 | 5.14 10.92 | 4.76 9.78 | 4.53 9.15 | 4.39 8.75 | 4.28 8.47 | 4.21 8.26 | 4.15 8.10 | 4.10 7.98 | 4.06 7.87 | 4.03 7.79 | 4.00 7.72 | 3.94 7.56 |
7 | .05 .01 | 5.59 12.25 | 4.74 9.55 | 4.35 8.45 | 4.12 7.85 | 3.97 7.46 | 3.87 7.19 | 3.79 7.00 | 3.73 6.84 | 3.68 6.71 | 3.63 6.62 | 3.60 6.54 | 3.57 6.47 | 3.51 6.31 |
8 | .05 .01 | 5.32 11.26 | 4.46 8.65 | 4.07 7.59 | 3.84 7.01 | 3.69 6.63 | 3.58 6.37 | 3.50 6.19 | 3.44 6.03 | 3.39 5.91 | 3.34 5.82 | 3.31 5.74 | 3.28 5.67 | 3.22 5.52 |
9 | .05 .01 | 5.12 10.56 | 4.26 8.02 | 3.86 6.99 | 3.63 6.42 | 3.48 6.06 | 3.37 5.80 | 3.29 5.61 | 3.23 5.47 | 3.18 5.35 | 3.14 5.26 | 3.10 5.18 | 3.07 5.11 | 3.01 4.96 |
10 | .05 .01 | 4.96 10.04 | 4.10 7.56 | 3.71 6.55 | 3.48 5.99 | 3.33 5.64 | 3.22 5.39 | 3.14 5.21 | 3.07 5.06 | 3.02 4.95 | 2.97 4.85 | 2.94 4.78 | 2.91 4.71 | 2.85 4.56 |
20 | .05 .01 | 4.30 7.95 | 3.44 5.72 | 3.05 4.82 | 2.82 4.31 | 2.66 3.99 | 2.55 3.76 | 2.46 3.59 | 2.40 3.45 | 2.34 3.35 | 2.30 3.26 | 2.31 3.30 | 2.28 3.23 | 2.20 3.09 |
30 | .05 .01 | 4.17 7.56 | 3.32 5.39 | 2.92 4.51 | 2.69 4.02 | 2.53 3.70 | 2.42 3.47 | 2.33 3.30 | 2.27 3.17 | 2.21 3.07 | 2.16 2.98 | 2.12 2.90 | 2.09 2.84 | 2.01 2.70 |
40 | .05 .01 | 4.08 7.31 | 3.23 5.18 | 2.84 4.31 | 2.61 3.83 | 2.45 3.51 | 2.34 3.29 | 2.25 3.12 | 2.18 2.99 | 2.12 2.89 | 2.08 2.80 | 2.04 2.73 | 2.00 2.66 | 1.92 2.52 |
50 | .05 .01 | 4.03 7.17 | 3.18 5.06 | 2.79 4.20 | 2.56 3.72 | 2.40 3.41 | 2.29 3.19 | 2.20 3.02 | 2.13 2.89 | 2.07 2.78 | 2.03 2.70 | 1.98 2.62 | 1.95 2.56 | 1.87 2.42 |
60 | .05 .01 | 4.00 7.08 | 3.15 4.98 | 2.76 4.13 | 2.53 3.65 | 2.37 3.34 | 2.25 3.12 | 2.17 2.95 | 2.10 2.82 | 2.04 2.72 | 1.99 2.63 | 1.95 2.56 | 1.92 2.50 | 1.84 2.35 |
70 | .05 .01 | 3.98 7.01 | 3.13 4.92 | 2.74 4.08 | 2.50 3.60 | 2.35 3.29 | 2.23 3.07 | 2.14 2.91 | 2.07 2.77 | 2.01 2.67 | 1.97 2.59 | 1.93 2.51 | 1.89 2.45 | 1.82 2.32 |
80 | .05 .01 | 3.96 6.96 | 3.11 4.88 | 2.72 4.04 | 2.48 3.56 | 2.33 3.25 | 2.21 3.04 | 2.12 2.87 | 2.05 2.74 | 1.99 2.64 | 1.95 2.55 | 1.91 2.48 | 1.88 2.41 | 1.80 2.28 |
100 | .05 .01 | 3.94 6.90 | 3.09 4.82 | 2.70 3.98 | 2.46 3.51 | 2.31 3.21 | 2.19 2.99 | 2.10 2.82 | 2.03 2.69 | 1.97 2.59 | 1.93 2.50 | 1.88 2.43 | 1.85 2.36 | 1.77 2.22 |
200 | .05 .01 | 3.89 6.76 | 3.04 4.71 | 2.65 3.88 | 2.42 3.41 | 2.26 3.11 | 2.14 2.89 | 2.06 2.73 | 1.98 2.60 | 1.93 2.50 | 1.88 2.41 | 1.83 2.34 | 1.80 2.28 | 1.72 2.13 |
400 | .05 .01 | 3.86 6.70 | 3.02 4.66 | 2.62 3.83 | 2.39 3.36 | 2.23 3.06 | 2.12 2.85 | 2.03 2.69 | 1.96 2.55 | 1.90 2.46 | 1.85 2.37 | 1.81 2.29 | 1.78 2.23 | 1.70 2.08 |
1000 | .05 .01 | 3.85 6.66 | 3.00 4.63 | 2.61 3.80 | 2.38 3.34 | 2.22 3.04 | 2.11 2.82 | 2.02 2.66 | 1.95 2.53 | 1.89 2.43 | 1.84 2.34 | 1.80 2.26 | 1.76 2.20 | 1.68 2.06 |
Inf | .05 .01 | 3.85 6.64 | 2.99 4.60 | 2.60 3.78 | 2.37 3.32 | 2.21 3.02 | 2.09 2.80 | 2.01 2.64 | 1.94 2.51 | 1.88 2.41 | 1.83 2.32 | 1.79 2.24 | 1.75 2.18 | 1.66 2.03 |
Phil Ender, 26Jan98