Read This Description of a Study and Answer the Question

Essay

Read this description of a study and answer the question that follow.
A reporter at a university newspaper sought to gather evidence about the quality of teaching at the university.For one week at the beginning of the semester she attended 5 different,large-lecture classes each day,each with a different instructor.She asked 4 other reporters to do this too (they all attended different classes),and she trained them regarding the ratings they would make.The reporters pretended to be students,but sat in the back of class so the instructor wouldn't notice their observations.Using 10-point rating scales,they rated each instructor on five dimensions: interesting,organized,informative,friendly,and respectful.They summarized their findings and reported that,in general,the quality of teaching at the university is very good.
Identify one aspect of the procedures in this study that the reporter used to improve the reliability of the observations.