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. 2016 May 20;2(1):e24. doi: 10.2196/publichealth.4967

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©Jennifer Nguyen, Michael Moorhouse, Barbara Curbow, Juliette Christie, Kim Walsh-Childers, Sabrina Islam. Originally published in JMIR Public Health and Surveillance (http://publichealth.jmir.org), 20.05.2016.

This is an open-access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work, first published in JMIR Public Health and Surveillance, is properly cited. The complete bibliographic information, a link to the original publication on http://publichealth.jmir.org, as well as this copyright and license information must be included.

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Person ability item-difficulty match of the college sample. Persons are on the left of the line, whereas the item difficulty map is to the right of the line. Each “O” represents 1-2 individuals, whereas each “X” represents 3 persons.