Week 6 Flashcards
what is the ranking of the hierarchy of study designs based on their contribution to causal inference from least to most?
case series -> cross-sectional -> case-control -> cohort -> RCT
which forms of bias should be considered in a RCT?
selection bias, performance bias, attrition bias, and detection bias
how do we control for selection bias?
randomized selection
allocation concealing
how do we control for performance bias?
blinding participants
how do we control for detection bias?
blinding outcome assessors
how do we control for attrition bias?
how was missing data dealt with? hard to control for, but should be considered when interpreting data
how do we control for reporting bias?
determine the factors that could result in reporting bias. reflecting on how under or over reporting may occur
identify the 2 ways standardized reporting was mandated
The Uniform Requirements for Manuscripts Submitted to Biomedical Journals
Consolidated Standards of Reporting Trials (CONSORT)
what are the downsides to simple randomization?
it is less efficient and there’s potential for group imbalance in small trials
what factors are considered inappropriate ways to randomize participants?
-test result
-alternating presentation
-case record number
-date of presentation
-age or birthday
what is stratified randomization?
study participants are stratified by prognostic factors (gender, age, etc) to reduce group imbalance in smaller trials
what is block randomization?
population is split up to account for the effects of a particular variable
ex. group 1 are smokers, they are evenly distributed into treatment group and control group. group 2 are nonsmokers and they are also evenly distributed into treatment group and control group
define what minimization means in a study
a complex computer-based method of allocating subjects into balanced groups based on key characteristics
T/F allocation concealment is different than blinding
true
when does blinding of a study occur? what bias does it prevent?
after subject allocation has been completed and is intended to occur throughout the entire duration of the study to prevent performance and detection bias
when does allocation concealment of a study occur? what bias does it prevent?
during allocation to prevent selection bias
T/F allocation concealment is always achievable
true
T/F blinding is not always achievable
true
what form of bias does triple-blinding help prevent?
reporting bias
define selection bias
when can it occur during a trial?
Systematic differences between baseline characteristics in the groups being compared
during allocation
define performance bias
when can it occur during a trial?
Systematic differences in the care provided to study participants apart from the intervention
during treatment intervention
define attrition bias
when can it occur during a trial?
how can it occur?
systematic differences in withdrawals from trial
during followup
drop-out participants or missing data (loss to followup)
define detection bias
when can it occur during a trial?
how can it occur?
systematic differences in outcome assessment
during outcome collection (end of trial)
if someone knows or figures out the intervention (treatment or placebo) which can consciously or unconsciously affect the trial outcome
an example of attrition bias is incomplete outcome data, what might cause this outcome?
trial stopped early
participants missing outcome assessment appointment
incomplete documentation from participants
