This would explain why amateurs won a majority of the prizes. If more photographs were entered by amateurs, amateurs as a collective had more chances to win prizes than professionals did.

This would explain the amateurs’ success. If the judges had a preference for amateur photographs, they would be more likely to award prizes to amateur entrants than to professional entrants.

This would explain why amateurs won more prizes than professionals. If amateurs submitted their best work and professionals did not, the quality of amateur photographs entered may have exceeded the quality of the professional photographs entered.

This would explain why amateurs won a majority of the prizes. If most of the prizes were open only to amateurs, then amateurs were bound to win a majority of them.

This provides no information about the number of amateur entrants relative to the number of professional entrants. It is still possible more professionals entered the contest than amateurs, in which case the outcome remains unexplained.