Sensitivity and Specificity of Single Near-Perfect (One Mismatch Allowed) Nucleotide K-mer Matches as a Search Criterion
| 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | |
| A. 81% | 0.945 | 0.880 | 0.831 | 0.721 | 0.657 | 0.526 | 0.465 | 0.408 | 0.356 | 0.255 | 0.218 |
| 83% | 0.975 | 0.936 | 0.904 | 0.820 | 0.770 | 0.649 | 0.591 | 0.535 | 0.480 | 0.361 | 0.318 |
| 85% | 0.991 | 0.971 | 0.954 | 0.900 | 0.865 | 0.767 | 0.719 | 0.669 | 0.619 | 0.490 | 0.445 |
| 87% | 0.997 | 0.990 | 0.983 | 0.954 | 0.935 | 0.867 | 0.833 | 0.796 | 0.757 | 0.634 | 0.591 |
| 89% | 1.000 | 0.997 | 0.995 | 0.984 | 0.976 | 0.939 | 0.920 | 0.897 | 0.872 | 0.775 | 0.741 |
| 91% | 1.000 | 1.000 | 0.999 | 0.996 | 0.994 | 0.979 | 0.971 | 0.962 | 0.950 | 0.890 | 0.869 |
| 93% | 1.000 | 1.000 | 1.000 | 0.999 | 0.999 | 0.996 | 0.994 | 0.991 | 0.988 | 0.963 | 0.954 |
| 95% | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 0.999 | 0.999 | 0.999 | 0.994 | 0.992 |
| 97% | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 | 1.000 |
| B. K | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 |
| F | 275671 | 68775 | 17163 | 4284 | 1070 | 267 | 67 | 17 | 4.2 | 1.0 | 0.3 |
[i] (A) Columns are for K sizes of 12–22. Rows represent various percentage identities between the homologous sequences. The table entries show the fraction of homologies detected as calculated by equation 6 assuming a homologous region of 100 bases. (B) K represents the size of the near-perfect match. F shows how many perfect matches of this size expected to occur by chance according to equation 7 in a genome of 3 billion bases using a query of 500 bases.