EPIDEMIOLOGY EQUATIONS Flashcards
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when RR>1, what does this mean?
risk of developing HRE is higher than the control group
when RR=1, what does this mean?
risk of developing HRE is the same as the control group
when RR<1, what does this mean?
risk of developing HRE is less than the control group
when what is the equation for relative risk?
risk of HRE in treatment group/risk of HRE in control group
when OR>1, what does this mean?
outcome of control is better than that of intervention
when OR=1, what does this mean?
outcome of intervention is same as that of control
when OR<1, what does this mean?
outcome of intervention is better than that of control
when what is the equation for odds ratio?
odds of HRE in treatment group/odds of HRE in the control group
when HR=0.5, what does this mean?
at any given time, half as many individuals in the intervention group are experiencing an event compared to the control group
when HR=1, what does this mean?
at any given time, the same number of individuals in the intervention group are experiencing an event as in the control group
when HR=2, what does this mean?
at any given time, twice the number of individuals in the intervention group are experiencing an even compared to the control group
when LR=0-1, what does this mean?
decreased evidence for HRE
when LR>1, what does this mean?
increased evidence for HRE
what is the equation for likelihood ratio?
probability a person with HRE has a specified test result/probability a person without HRE has a specific test result
when LR+>10, what does this mean?
test result has large effect on increasing probability of HRE
when LR+=5-10, what does this mean?
test result has moderate effect on increasing probability of HRE
when LR+<5, what does this mean?
test result has small effect on increasing probability of HRE
Positive likelihood ratio (LR+) equation?
LR+=sensitivity/(1-specificity)
when LR-<0.1, what does this mean?
test result has large effect on decreasing probability of HRE
when LR-=0.5-0.1, what does this mean?
test result has moderate effect on decreasing probability of HRE
when LR->0.5, what does this mean?
test result has small effect on decreasing probability of HRE
Negative likelihood ratio (LR-) equation?
LR-=(1-sensitivity)/specificity
relative risk equation?
RR=(A/(A+B))/(C/(C+D))
odds ratio equation?
OR=(AxD)/(BxC)
sensitivity equation?
sensitivity=A/(A+C)
specificity equation?
specificity=D/(B+D)
postive predictive value?
PPV=A/(A+B)
negative predictive value?
NPV=D/(C+D)
calculating numbers to treat
experimental event rate equation?
control event rate equation?
absolute risk reduction equation equation?
NNT equation?
A/A+B
C/C+D
CER-EER
1/ARR
calculating numbers needed to harm
experimental event rate equation?
control event rate equation?
absolute risk reduction equation equation?
NNT equation?
A/A+B
C/C+D
CER-EER
1/ARI
ARI=absolute difference between CER and EER
