Prof. Ortiz is conducting a study of children's peer interactions in the school lunchroom. To expedite the research process, Dr. Ortiz has decided to collect his own observational data (rather than train somebody who does not know the research question and hypothesis) because he is already familiar with the study's hypotheses.
1. Because he is aware of the purpose of the study, Dr. Ortiz is risking ___________.a) practice effortsb) observer influencec) observer biasd) biased sampling