Measures of Effect Flashcards
Which ratios are relative measures of effect?
Risk Ratio & Odds Ratio
What is the definition of relative measures of effect?
They describe how an exposure changes the risks or odds of an outcome compared to the risks and the odds of an unexposed group
Which are the examples of absolute measures of effect?
Absolute risk
Number needed to treat
What is the calculation of risk ratio/relative risk?
Risk of exposed/Risk of unexposed
What is the interpretation of a RR < 1?
The risk of a certain outcome is lower in the exposed group than it is in the unexposed
What is the interpretation of RR > 1?
The risk of a certain outcome is higher in the exposed group compared to the unexposed group; exposure is a risk factor for the outcome
What is the interpretation of a risk ratio = 1?
This means there is no difference at all between the risk of the exposed vs. the unexposed groups
What is a confidence interval?
It is the range with whichin the actually risk ratio lies in with a probability of 95%
When is the difference between two groups statistically significant?
If the confidence interval does not include 1
What is the definition of risk?
The probability of an outcome which can be both positive or negative
How would you interpret an RR of 1.5?
The risk of the exposed group getting affected is 1.5 times greater than the risk of unexposed people getting affected, or 50% higher
What is the calculation for relative risk difference?
Risk Ratio - 1
What is absolute risk difference?
Risk of exposed group - Risk of unexposed group
What is the calculation for Odds Ratio?
Odds of exposed group/ Odds of unexposed group
What is the Odds Ratio?
Relative measure of effect
What is the definition of “Odds”?
The chance of having a certain outcome
What is the interpretation of OR < 1?
The chance of a certain outcome is lower in exposed group
What is the interpretation of OR > 1?
The chance of a certain outcome is greater in the exposed group
What is the interpretation of OR = 1?
There is no difference for the chance of a certain between an exposed group vs an unexposed one
When does the CI of Odds Ratio show statistical significance?
When the Odds Ratio does not contain 1
What is the difference between risks and odds calculations?
To find the risk of an outcome –> people with an outcome/all people
To find the odds of an outcome –>
people with an outcome/people WITHOUT an outcome
What are the differences between RR and OR?
OR –> all study types, more often used for case-control
RR –> cannot be used for case-control studies
Interpretation of RR is easier than OR, so RR is preferred
In which cases are RR and OR very similar?
When the outcome is really rare