At the 2015 IMO held in Chiang Mai, Thailand, 577 contestants from 104 countries competed. 39 gold medals were awarded to those scoring at least 26; 100 silver medals were awarded to those scoring from 19 to 25; and 143 bronze medals were awarded to those scoring from 14 to 18.
Further statistics are shown below. Detailed tables of results by country or contestant are available:
The maximum individual score possible was 42 (which only one contestant attained). The mean individual score was 12.981, with a standard deviation of 8.288. The following table shows how many contestants attained each possible score.
| Score | Number of contestants |
|---|---|
| 42 | 1 |
| 41 | 1 |
| 40 | 1 |
| 39 | 0 |
| 38 | 0 |
| 37 | 0 |
| 36 | 1 |
| 35 | 3 |
| 34 | 1 |
| 33 | 0 |
| 32 | 1 |
| 31 | 7 |
| 30 | 2 |
| 29 | 7 |
| 28 | 6 |
| 27 | 5 |
| 26 | 3 |
| 25 | 15 |
| 24 | 3 |
| 23 | 18 |
| 22 | 12 |
| 21 | 13 |
| 20 | 17 |
| 19 | 22 |
| 18 | 20 |
| 17 | 23 |
| 16 | 34 |
| 15 | 40 |
| 14 | 26 |
| 13 | 24 |
| 12 | 15 |
| 11 | 15 |
| 10 | 28 |
| 9 | 29 |
| 8 | 26 |
| 7 | 11 |
| 6 | 18 |
| 5 | 16 |
| 4 | 15 |
| 3 | 28 |
| 2 | 24 |
| 1 | 21 |
| 0 | 25 |
The following table shows the maximum attainable score, mean score and standard deviation of scores for each individual question.
| Question number | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|
| Maximum score | 7 | 7 | 7 | 7 | 7 | 7 |
| Mean score | 4.307 | 1.359 | 0.653 | 4.794 | 1.513 | 0.355 |
| Standard deviation | 2.870 | 1.914 | 1.605 | 2.905 | 1.709 | 1.294 |
The following table shows the correlation coefficients between the scores on each pair of questions. To make sense of these figures you will probably wish to look at the problems themselves (from Mathlinks) to see which are on similar or different topics.
| 1 | 2 | 3 | 4 | 5 | 6 | |
|---|---|---|---|---|---|---|
| 1 | 0.378 | 0.249 | 0.450 | 0.385 | 0.211 | |
| 2 | 0.378 | 0.363 | 0.377 | 0.476 | 0.278 | |
| 3 | 0.249 | 0.363 | 0.272 | 0.333 | 0.288 | |
| 4 | 0.450 | 0.377 | 0.272 | 0.357 | 0.148 | |
| 5 | 0.385 | 0.476 | 0.333 | 0.357 | 0.172 | |
| 6 | 0.211 | 0.278 | 0.288 | 0.148 | 0.172 |
The following table shows the distribution of scores on each individual question with the total number of each score on any question.
| Score 0 | Score 1 | Score 2 | Score 3 | Score 4 | Score 5 | Score 6 | Score 7 | |
|---|---|---|---|---|---|---|---|---|
| Question 1 | 93 | 89 | 5 | 21 | 72 | 12 | 20 | 265 |
| Question 2 | 256 | 151 | 77 | 27 | 8 | 13 | 14 | 31 |
| Question 3 | 408 | 122 | 12 | 1 | 3 | 0 | 1 | 30 |
| Question 4 | 91 | 36 | 61 | 18 | 11 | 1 | 8 | 351 |
| Question 5 | 153 | 255 | 34 | 90 | 8 | 4 | 3 | 30 |
| Question 6 | 521 | 11 | 15 | 6 | 3 | 3 | 7 | 11 |
| Total | 1522 | 664 | 204 | 163 | 105 | 33 | 53 | 718 |
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