To illustrate exactly how improbable a given IQ score might be, see the following table of statistics on below average IQs. Scores are from the Stanford-Binet test, the original and best-known IQ test — see here. They follow a normal (bell curve) distribution with a mean of 100 points and a standard deviation of 15 points.
| IQ | Occurrence | Frequency | On Earth (of 7 500 000 000) |
| ≤100 | 50% | 1 in 2 | 3 750 000 000 |
| ≤ 95 | 37% | 1 in 3 | 2 770 810 051 |
| ≤ 90 | 25% | 1 in 4 | 1 893 694 032 |
| ≤ 85 | 16% | 1 in 6 | 1 189 914 404 |
| ≤ 80 | 09.1% | 1 in 11 | 684 084 148 |
| ≤ 75 | 04.8% | 1 in 21 | 358 427 642 |
| ≤ 70 | 02.3% | 1 in 44 | 170 625 990 |
| ≤ 65 | 00.98% | 1 in 102 | 73 614 965 |
| ≤ 60 | 00.38% | 1 in 261 | 28 727 854 |
| ≤ 55 | 00.13% | 1 in 741 | 10 124 235 |
| ≤ 50 | 00.043% | 1 in 2 331 | 3 217 952 |
| ≤ 45 | 00.012% | 1 in 8 139 | 921 498 |
| ≤ 40 | 00.003 2% | 1 in 31 574 | 237 534 |
| ≤ 35 | 00.000 73% | 1 in 136 176 | 55 076 |
| ≤ 30 | 00.000 15% | 1 in 653 327 | 11 480 |
| ≤ 25 | 00.000 029% | 1 in 3 488 556 | 2 150 |
| ≤ 20 | 00.000 004 8% | 1 in 20 741 279 | 362 |
| ≤ 15 | 00.000 000 73% | 1 in 137 360 560 | 55 |
| ≤ 10 | 00.000 000 099% | 1 in 1 013 594 692 | 7 |
| ≤ 5 | 00.000 000 012% | 1 in 8 336 096 322 | 1 |
| ≤ 0 | 00.000 000 001 3% | 1 in 76 429 666 480 | 0 |
