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Lecture 16

# PUBHLTH 101 Lecture Notes - Lecture 16: Recall Bias, Observational Error, Sampling Error

by OC2443940

Department

Public HealthCourse Code

PUBHLTH 101Professor

David TimberlakeLecture

16This

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SPURIOUS ASSOCATIONS

1. Random error/chance: An alpha level of 0.05 leaves a 1/20 chance of a false-positive

result

2. Systematic (non-random) error: Bias which can occur in a study design, conducting or

analysis of an epidemiologic study

Ex. Recall bias in data collection

CAUSAL ASSOCIATIONS:

• Casual associations are REAL associations which are causal

• In epidemiology, it is difficult to prove a casual association, particularly for

observational studies

THE WEB OF CAUSATION

• Not single cause

• Causes of disease are interacting

• Illustrates the interconnection

CONSISTENCY

• Associations are more likely to be causal if they are observed repeatedly by different

persons, in different places , circumstances and time.

• Ex. Meta-analysis of studies of lung cancer of never-smoking females exposed to

spousal smoking, by continent

To show a valid statistical association, we need to assess:

• Random error: deviation of results and inferences from the truth, occurring only as a

result of chance

1. Measurement error: due to inexact measuring instruments, subjective measures,

must be random

2. Sampling error: can be assessed w/ confidence intervals, can be reduced w/ a larger

sample size

• Systematic error (bias): process at any state of inference

1. Underestimate/overestimate the true effect

2. Produce a spurious association

3. Distort apparent direction of an association

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