Information Bias

Question 1

What is information bias?

Answer 1

Information bias is an observation or information bias results from systemic differences in the way data on exposure or outcome are obtained from the various study groups

Question 2

How can measurement error occur?

Answer 2

Objective measures don’t require recall to be made whereas subjective measures do
Measurement error can occur if participants prove inaccurate response or data is collected incorrectly/inaccurately (forget past exposures, problem with measuring device)
Want data to be collected in the same way for all the people in the study

Question 3

What effect might measurement error have?

Answer 3

Descriptive study: could over/underestimate prevalence
Analytic study: can lead to misclassification. People without the exposure may be classified as having the explore and vice versa. People without the outcome may be classified as having the outcome

Question 4

What is non-differential misclassfication?

Answer 4

When measurement error and any resulting misclassification occurs equally in all groups being compared

Question 5

What is differential misclassification?

Answer 5

Differences between the study groups e.g. exposed/comparison group, or case-controls
Example: in a cross sectional study, people with the outcome might report the exposure differently to those without the outcome

Question 6

What is recall bias?

Answer 6

Systematic error due to differences in accuracy or completeness of recall to memory of past events or experiences
Consider: who is the outcome effecting, how it affects people and what effect it has on the measure of association

Question 7

How does differential misclassification affect cohort studies?

Answer 7

If classification of exposure depends on outcome - BUT outcome not yet happened in a prospective cohort study; can be historical
If classification of outcome depends on the exposure - interviewer/observer bias

Question 8

How can we minimise information bias?

Answer 8

Use valid survey instruments, validate using objective measures, use standardised and calibrated equipment. Use blinding, structured interviews and standardised prompts, train the interviewers

Question 9

What is publication bias?

Answer 9

The result of the tendency of authors to submit, organisations to encourage, reviewers to approve and editors to publish articles containing positive findings