Learning Objectives

A. Describe key features of the two types of bias and give examples of each:

  1. Selection Bias
    • Define selection bias
    • Describe types of selection bias
      1. Control-selection bias
      2. Self-selection bias
      3. Loss to follow-up
      4. Differential surveillance, diagnosis or referral bias
  1. Observation/Information Bias:
    • Define observation bias
    • Describe types of observation bias
      1. Recall bias
      2. Interviewer bias
      3. Differential and non-differential misclassification

B. Identify types of biases specific for different study designs:

  1. Randomized clinical trials (RCT)
  2. Case-control studies
  3. Cohort studies

C. Understand how the magnitude and direction of bias can affect study results

D. Describe ways to minimize bias in the design phase of a study:

  1. Develop an explicit case definition
  2. Enroll all cases in a defined time and region from a defined source population
  3. Strive for high participation rate (minimize loss to follow-up and drop-out rate)
  4. Take precautions to ensure your sample is a good representation of the underlying population
  5. Handling of misclassification (observer bias, measurement bias)
  6. Other methods