FIGURE A-6 Categories of research.

FIGURE A-7 Facilities/location of studies.

Number and Demographics of Research Participants

The number of participants in a published article ranged from 1 to 336,668. Most studies (272) included 1,000 or fewer participants (Figure A-9).

Gender More studies included male participants than female participants (Figure A-10).

Age Most studies included adult participants; few included participants younger than 18 years (Figure A-11).

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