1. The study authors used stringent sampling methods in this multicenter study to avoid systematic error. What specific type of bias were they trying to avoid? (2 points) A. Reporting bias B. Selection bias C. Recall bias D. Interviewer bias 2. Suppose during sampling it turned out the authors sampled predominantly from schools in very high-income neighborhoods, but they had intended for the estimates to be applicable to middle school students of all household income levels. What would be the impact on the validity of the study? Answer in 1-2 sentences. (2 points) 3. While preparing the survey described above, the authors developed manuals of procedures and standardized intensive training for staff administering the surveys to participating students. What type of bias was this intended to avoid? (2 points) A. Selection bias B. Information bias