IMED2003 Study Guide - Midterm Guide: Smoking Age, Selection Bias, Effect SizePremium
2 pages57 viewsSpring 2018
DepartmentIntegrated Medical Sciences
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IMED2003: Revision 11 Notes
What is randomisation
●⇒ System for assigning study subjects to treatment groups that are independent
of the individual participants’ characteristics.
○ Each participant should have an equal chance of being assigned to any
● → Simple; stratified, block
Why do we randomise?
● Used to eliminate selection bias
○⇒ Removes systematic differences between the treatment and control
● Since it produces comparable groups, it may eliminate known and unknown
● Groups should have a similar spread of other characteristics
○ Eg. (sex, smoking age, weight etc.)
Intention to Treat Analysis:
● WHAT IS IT?
○ Once a patient is randomised they should be analysed in the treatment
group to which they were randomised to
○ EVEN if they actually received the alternative treatment or do not comply
with the treatment
○ Breaks the randomisation ⇒ introduces bias
○ Participants who adhere may be different from those who don’t in ways
that are related to the outcome
○ Effect size will reflect what likely to be seen in ‘real-world’ practice
○ Usually results in an underestimation of the treatment effect
Stopping Rules in Clinical Trials:
●⇒ Essential for most clinical trials
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