The document discusses threats to validity from information bias and selection bias in epidemiology studies. It explains key concepts like the difference between causal and error-based associations, internal and external validity, types of populations, and sources of information and selection bias. Specifically, it covers identifying sources of bias, understanding differential and non-differential misclassification and their implications, and strategies for minimizing biases in study design and analysis.

1. Threats to Validity: Information and Selection Bias
1. Understand the sources of association in epidemiology, i.e. causal vs. error
1. Understand the sources of error, i.e. random and systematic
2. Understand difference between precision and validity
3. Understand difference between internal and external validity
2. Know and understand the difference between external, target, actual, and study
populations
1. Understand for which populations findings from epidemiologic studies provide
inference and why
3. Understand the concept of information bias
1. Identify sources of information bias (e.g. interviewer bias, exposure or
outcome identification, misclassification)
2. Understand the difference between differential and non-differential
misclassification
i. Understand the implications of differential and non-differential
misclassification for your study findings in terms of direction of bias
4. Understand the concept of selection bias
i. Identify sources of selection bias in both case-control and cohort studies
5. Identify strategies for minimizing bias
1

2. Threats to Validity:
Information and Selection Bias
2

3. 3
Bias outline
• Big picture
• Sources of error
• Hierarchy of populations
• Types of validity
• Biases
– Information
– Selection
• Comparing biases
• Preventing biases
• Summary

4. Big picture
• Sources of association in epidemiology
– After analyzing epidemiologic data, you observe an
association between exposure and disease
– What are possible explanations for the association?
4

5. 5
Big picture
• Causal association
– Exposure causes disease
– This is typically what is of interest in an epidemiologic
study
– While causal effect may be behind an observed
association, other explanations must be considered
as well
– This unit is about considering other possible
explanations