Week 3 Flashcards
performance bias
systematic differences in the care provided to the comparison groups other than the intervention being tested
reducing performance bias
blinding
detection bias
outcome assessment differs systematically between comparison groups
reducing detection bias
blinding of outcome assessors
measurement bias
systematic error in the measurement of information on the exposure or outcome
measurement bias aka
information bias and observation bias
misclassification
incomplete medical records, recording errors, misinterpretation of records, errors in the questionnaire including recall bias by the participant
non differential misclassification
information is incorrect, but same across the two groups
underestimates the strength of association between exposure and disease
differential misclassifaction
information errors differ between the two groups
either a decrease or increase in the perceived association between exposure and outcome
reduce measurement bias
standardised research protocols, obtaining information from multiple sources, blinding of researchers and staff to the exposure/disease status of the participant, training of interviewers
reduce recall/response bias
defining research question carefully
devise high quality questionnaires
highly trained research staff
attrition bias
loses to follow up or dropouts
intention to treat analysis (ITT)
analysing all participants recruited from the randomisation process even if they have not completed the study
done to avoid the effects of crossover and dropout
methods for dealing with missing data
baseline values or last outcome measured by participant carries over
sensitivity analysis
mixed models
worst and best cases scenarios
reducing attrition bias
create project identity
good communication between staff and participants
keep follow up interviews brief
accessibility to clinics
