risk Flashcards
what is risk?
it is the probability of disease where 0 is impossible and 1 is certain
what does a probability of 0.5 means?
there is an equal probability of the disease occurring and not occurring
what is risk equation?
the chance something happens/the chance everything happens or the number of new cases/ the number at risk (risk is the occurrence of new cases in a population)
what do cohort studies do in relation to risk?
they try and establish risk factors/ causes - subgroups of population are selected based on their exposures and observed over time and then incidence rates of disease are calculated - allows risk to be calculated for the exposed an unexposed groups
what is the equation for risk ratio?
a/(a+c)/b(b+d) a = case with disease exposed to risk factor b = disease not exposed c = without disease but exposed d = without disease and unexposed
what is relative risk?
it is used to describe odds ratio, risk ratio and incidence rate ratio
what is the odds?
it is the probability or risk of a particular outcome happening = number of outcomes/total number of possible outcomes
what would ratio of 50:1 mean?
odds of 1/50 = 0.02
what is the odds ratio?
it is used to represent the relative risk for a case control study
what is the equation for odds ratio?
ad/bc or (a/c)/(b/d)
a and b are cases that are a) exposed and b) unexposed b c and d are controls that are c) exposed and d) unexposed
what is the value of odds and risk ratio in rare disease?
very similar
what does each value of relative risk mean?
1 = risk is same in exposed and unexposed
<1 = exposure = protective
>1 = exposure = harmful
very large or very small show stronger associations - NOT CAUSATION
how are units usually expressed in rare disease?
as rate per million
what must hypotheses be?
plausible, directional, precise and falsifiable
what must the research question be?
responsive, reliable and valid
