A case-control study is conducted to assess the relationship between poor diet and coronary artery disease. They enroll cases from cardiac floors in hospitals and controls from primary care physician offices in a single metropolitan area, Diet for the past 10 years was recorded using an in-person interview. On average, the dietary interview with cases lasted 30 minutes longer than the interview with controls. In addition, the information collected from cases was much more detailed. Which of the following type of bias most likely occurred?