Revision

Question 1

what is attributable risk (incidence difference)

Answer 1

the difference between the incidence in the exposed and that in the unexposed

incidence in exposed- incidence in unexposed
incidence of disease among exposed caused by the exposure
the frequency of disease attributable to exposure

Question 2

AR% (attributable proportion, attributable fraction, etiologic fraction)

Answer 2

the proportion of disease among the exposed which
- can be attributed to the exposure
- could be avoided by eliminating the exposure

incidence in exposed - incidence in unexposed

incidence in exposed

x 100

Question 3

population attributable risk

Answer 3

incidence of disease in a population attributable to the risk factor
absolute difference between risk in the total population and unexposed population

Question 4

limitations of cohort study

Answer 4

loss to follow up
requires large investment of time, and money
large sample size needed
reproducibility is hard
uncontrolled confounding

Question 5

intention to treat analysis

Answer 5

compares outcomes for all randomised individuals- even if they stop taking treatment or drop out of study

assesses the overall effect of assigning a subject to receive a particular intervention

analysis is the most important analysis as intervention and control groups compared as originally randomised

more likely to underestimate treatment effect
often use a modified ITT analysis- all randomised participants with some follow up data