lecture 25

Question 1

how can measurement error occur

Answer 1

• participants provide inaccurate responses
• data is collected incorrectly / inaccurately

Question 2

what effect might measurement error have in a descriptive study

Answer 2

could over / under estimate prevalence

Question 3

what effect might measurement error have in an analytic study

Answer 3

• can lead to misclassification
• people without the exposure may be classified as having the exposure
• people without the outcome may be classified as having the outcome

Question 4

what is non differential misclassification

Answer 4

‘not different’ between the study groups e.g exposed / comparison group or cases / controls

Question 5

what is differential misclassification

Answer 5

‘different’ between the study groups e,g exposed / comparison group or cases / controls

Question 6

example of differential misclassification in a cross sectional study for participants and interviewers

Answer 6

participant = people with the outcome might report the exposure differently to those without the outcome

interviewer = an interviewer who is aware they are interviewing a case might ask more probing questions about the exposure of interest

Question 7

example of differential misclassification in a case control study for participants and interviewers

Answer 7

participant = cases might more accurately recall past exposures compared to controls

interviewer = 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 8

what is the definition of recall bias

Answer 8

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

Question 9

how can you minimise interviewer bias

Answer 9

• clearly defined study protocol and measures
• structured questionnaire and standard prompts
• training of interviewers
• blinding

Question 10

how to minimise information bias from collecting information from participants

Answer 10

• validated survey instruments
• validate using objective measure

Question 11

what is selection bias

Answer 11

occurs when there is a systematic difference between the people who are included in a study and those who are not

Question 12

what is information bias

Answer 12

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

Question 13

what is publication bias

Answer 13

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