Epidemiology Chapter 9: Sources of Error

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Questions and Answers

Name the two basic types of error in epidemiologic research.

Systematic error and random error.

How do parameters differ from estimates?

Parameters cannot be calculated and are assumed to be error-free quantifications, whereas estimates are calculated using empirical data and are prone to error.

Provide a synonym for systematic error.

Bias

Provide a synonym for random error.

Imprecision Signup and view all the answers

Provide an antonym for biased.

Valid Signup and view all the answers

Provide an antonym for precise.

Imprecise Signup and view all the answers

List ways in which random error differs from systematic error.

Random error is balanced, decreases with sample size, and can be addressed with confidence intervals and p-values; systematic error is unbalanced, unaffected by sample size, and not addressed by routine statistical methods. Signup and view all the answers

Probability models are used to adjust for bias in epidemiologic studies. Explain your response.

False Signup and view all the answers

What are the two common forms of statistical inference?

Estimation and hypothesis (significance) testing. Signup and view all the answers

How would expanding the sample size of an observational study affect random error and systematic error?

Expanding the sample size will decrease random error and have no effect on systematic error. Signup and view all the answers

Name the three general categories of bias in epidemiologic research.

Selection bias, information bias, confounding bias. Signup and view all the answers

What is the effect of nondifferential misclassification on measures of association?

Nondifferential misclassification biases measures of association either toward the null or not at all. Signup and view all the answers

A bias toward null means that the observed measure of association will underestimate the true risks or benefits associated with exposure.

True Signup and view all the answers

Define confounding.

Confounding is a distortion in a measure of association brought about by extraneous factors 'lurking' in the background. Signup and view all the answers

List the properties of a confounder.

(1) Associated with the exposure, (2) Independent risk factor for disease, (3) Not intermediate in the causal pathway. Signup and view all the answers

What does the Latin word confundere mean?

To mix-up. Signup and view all the answers

Use of hospitalized cases and controls in case-control studies could result in what type of bias?

Hospital admission rate bias, also known as Berkson's bias. Signup and view all the answers

If cases in a case-control study provide more complete responses about exposures to potential risk factors than controls, what type of bias will this cause?

Recall bias, and the odds ratio will be biased away from the null. Signup and view all the answers

If the code book for a data set gets mixed-up so that exposed individuals are mistakenly coded as nonexposed and vice versa, what type of bias will this cause?

Information or misclassification bias. Signup and view all the answers

Not all risk factors are confounders. Why?

A risk factor that is equally distributed in the groups being compared will not confound the results, and a risk factor that is intermediate in the causal pathway should not be considered a confounder. Signup and view all the answers

Why can the results of a study on smoking and lung cancer in men be generalized to the effects of smoking on lung cancer in women?

The causal mechanisms of lung cancer are similar in men and women. Signup and view all the answers

Confidence intervals adjust for both random and systematic sources of error providing confidence in the study's results.

False Signup and view all the answers

Study Notes

Types of Error in Epidemiology

Two basic types of errors: systematic error (bias) and random error (imprecision).
Bias is an unbalanced error that affects study validity, while random error can be reduced by increasing sample size.

Parameters vs. Estimates

Parameters are assumed to be error-free quantifications, while estimates are calculated from empirical data and subject to errors.

Bias and Precision

Synonyms: Systematic error is synonymous with bias, and random error with imprecision.
Antonyms: The antonym of biased is valid, and the antonym of precise is imprecise.

Characteristics of Errors

Random error is balanced, decreases with larger sample sizes, and can be addressed using statistical methods like confidence intervals.
Systematic error remains unaffected by sample size, and common statistical methods do not correct it.

Statistical Inference

Two main forms of statistical inference: estimation and hypothesis testing.

Impact of Sample Size

Increasing sample size reduces random error but has no effect on systematic error.

Types of Bias

Three general categories of bias in epidemiology: selection bias, information bias, and confounding bias.

Nondifferential Misclassification

This type of misclassification biases measures of association either toward the null or does not bias them at all.

Bias Toward the Null

A bias toward the null underestimates the true risks or benefits associated with an exposure.

Confounding Definition and Properties

Confounding: Distortion in a measure of association caused by extraneous factors.
Properties of a confounder: Must be associated with exposure, an independent risk factor for disease, and not intermediate in the causal pathway.

Hospitalization Bias

Using hospitalized cases and controls in a case-control study may lead to hospital admission rate bias (Berkson's bias).

Recall Bias

When cases provide more complete exposure responses than controls, it results in recall bias, which biases results away from the null.

Misclassification Bias

Mixing up codes for exposed and non-exposed individuals results in information or misclassification bias.

Risk Factors and Confounding

Not all risk factors are confounders; only those associated with exposure and not equally distributed across groups or part of the causal pathway are considered confounders.

Generalizability of Findings

Findings from studies on smoking and lung cancer in men can be applied to women due to similar causal mechanisms of the disease.

Confidence Intervals

Confidence intervals only address random error and do not adjust for systematic sources, which limits their ability to provide overall validity in study results.

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Description

Test your knowledge on the sources of error in epidemiologic research with this flashcard quiz. Covering fundamental concepts such as systematic and random errors, as well as the distinction between parameters and estimates, this quiz is perfect for students of epidemiology.