Exam 3: Validity, Bias, and Confounding Flashcards
What is external validity?
The meaning of the study to the intended population
Requires internal validity
What is internal validity?
Correct assessment of exposure and outcome in study groups
Concerns the formation of the comparison groups and measurement of exposure and disease
Does internal validity require external validity?
No
What is bias?
A systematic error that results in an incorrect estimate in the relationship between exposure and disease
What does bias do the results if it is uncorrected?
It renders them worthless
What is selection bias?
Concerns the animals who participate and those that do not
If the study involves treatment, who receives what treatment
Do the animals reflect the target population
Comparisons must be drawn from the same population
What is information bias?
Assessment of exposures and outcomes
Types: observer bias, recall bias, misclassification
What is observer bias?
Differences in the way information collected from E+ vs E- or D+ vs D-
What is recall bias?
Those D+ may tend to recall exposures in greater detail than those D-
What is misclassification?
When either E or D is not properly classified
What is confounding?
A “mixing” of effects
What is a confounding variable (confounder)?
An extraneous variable that can wholly or partly account for an apparent association between an exposure and outcome
Produces spurious association or masks real association
Correlated with the explanatory and response variables
How can you control confounding?
Restriction
Matching
Analysis (stratification, multivaribale techniques)
What is restriction?
Restrict study subjects to avoid known confounding factors
What is matching?
Match pairs on a confounding variable so that confounding is distributed evenly between comparands
