One of the authors wanted to determine the effect of changing answers on​ multiple-choice tests. she studied the tests given by another​ professor, who had told his students before their exams that if they had doubts about an answer they had​ written, they would be better off not changing their initial answer. the author went through the exams to look for​ erasures, which indicate that the first choice was changed. in these​ tests, there is only one correct answer for each question. use the bar chart to answer the question below.