I have conducted an experiment in which 3 groups of 20 participants each had 15 multiple choice questions (3 to choose from each time: 1 correct answer and two distractors).

I am interested in the results from one of the groups (they got 147 answers correct out of 300) but need to prove that these 147 selections were not down to chance. I am not sure which tests to run or how to present this information in the correct statistical format. Is anybody please able to advise? TIA