Critical Thinking - Lecture Twenty-Six

Question 1

Information bias

Answer 1

The observation or information bias results from systematic differences in the way data on exposure or outcome are obtained from the various study groups

Question 2

How is data collected in a study?

Answer 2

By participants, collected or measured by someone else

Question 3

How can measurement error occur

Answer 3

Participants provide inaccurate responses or data is collected incorrectly/inaccurately

Question 4

What effect might measurement error have in a descriptive study?

Answer 4

Could over/underestimate prevalence

Question 5

What effect might measurement error have in an analytical study?

Answer 5

People without the exposure may be classified as having the exposure (vice versa)
People without the outcome may be classified as having the outcome (vice versa)

Question 6

Types of misclassification

Answer 6

Non-differential and differential

Question 7

Non-differential misclassification

Answer 7

Not different between the study groups. Non-differential misclassification is when measurement error and any resulting misclassification occur equally in all groups being compared, they are described as being non-differential

Question 8

Differential misclassification

Answer 8

Different between the study groups

Question 9

Examples of differential misclassification

Answer 9

In a cross-sectional study, people with the outcome might report the exposure differently to those without the outcome
In a case-control study, cases might more accurately recall past exposures compared to controls
In a case-control study, an interviewer who is aware they are interviewing a case might ask more probing questions about the exposure of interest
In a cohort study, an interviewer aware of the exposure status may ask more probing questions about the outcome among those exposed compared with those in the comparison group

Question 10

Recall bias

Answer 10

Systematic error due to differences in accuracy or completeness of recall to memory of past events or experiences

Question 11

Minimising recall bias

Answer 11

Objective measures, validate self-reported measures with outer information and memory aids

Question 12

Differential misclassification in cohort studies

Answer 12

If classification of exposure depends on outcome (BUT outcome not yet happened in a prospective cohort study; can be an issue in historical cohort studies)
If classification of outcome depends on the exposure e.g. if interviewer/observer knew the exposure status and examined the outcome differently for those in the exposed group compared with those in the comparison group

Question 13

Minimising interviewer/observer bias examples

Answer 13

Clearly defined study protocol and measures, structured questionnaire and standard prompts, training of interviewers and blinding

Question 14

Bias in randomised controlled trials

Answer 14

Bias could occur if knowledge of the treatment/exposure category influences the assessment of the outcome
Bias could occur if measurements are undertaken differently for different treatment groups

Question 15

Minimising information bias in terms of measurement instruments

Answer 15

Use standardised equipment or calibrated equipment

Question 16

When minimising information bias, what is also important?

Answer 16

Having a clearly defined study protocol and well defined exposures, outcomes and other factors collected in the study

Question 17

Publication bias

Answer 17

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