Flashcards in Bias and Confounding Deck (28):
Relates to the absence of systematic error in a study
a valid measure of association
a study will have the same value as the true measure in the source population, except for error due to random variation
The extent to which a measure of association from a study differs from the true measure of association in the source population
What causes bias?
the study result is valid with respect to the population under study
the study result is valid to a wider population beyond the study population and/or source population
What is also called generalizability?
the subjects in the study
Population from which the subjects were drawn
population to which we may want to generalize our results
A bias that equally affects groups
a bias that affects one group or more than another
What are two general sources of bias?
error in selection of study subjects
error in measurement
Animals with no disease are classified as diseased
an unknown factor distorts the relationship between the exposure and outcome
Self Selection bias
studies based upon volunteers- may not be representative of the population as a whole
Diagnostic of disease may be influenced by the vet's knowledge of the exposure and their expectation of disease
Different observes interpret information differently
What are some examples of Information Bias?
Deficiency of tools and technical errors
Those affected by a disease have a greater sensitivity for recalling exposure
Individuals with severe disease tend to have more complete medical records
Selection Bias Examples
Three condition a confounder must meet
Associated with exposure
Associated with the outcome
Not in the causal pathway between the exposure and the outcome
How can you reduce confounding variables?
Match the study so the confounding factor is equally respresented
Restrict animals with the confounding factor
Partition the results based on the confounding factor