The owner of a professional sports team sent out questionnaires to evaluate how well the coaching staff was doing its job. A questionnaire was sent to a random sample of 150 ticket buyers and asked, How well do you think our hardworking and competent coaching staff of our young and inexperienced team is doing? Eighty percent (80%) of the questionnaires were returned. The responses came back with largely positive comments about the coaching staff. Why could the owner NOT conclude that sports fans approved of the job the coaching staff was doing? There was sampling bias because the owner took a convenience sample. This was only one survey and people's opinion changes over time. There is measurement bias. The question was worded in such a way that the respondents responses were influenced. There is nonresponse bias. The results could be biased because a small percentage who chose to return the survey might be very different from the majority who did not return the survey