29 Questions
What does a risk ratio compare?
The risk of a health event among one group with the risk of the same event in another group
What is used to quantify the relationship between an exposure and a particular disease?
Risk ratio
Inherent characteristics of persons, biologic characteristics, and acquired characteristics are examples of what?
Activities and conditions under which they live
What does an odds ratio compare?
The odds of a health event in one group to the odds of the same event in another group
What does a rate ratio compare?
The rate of a health event in one group to the rate of the same event in another group
What does a two-by-two table (contingency table) help to analyze?
The relationship between exposure and outcome in two groups
What does the attributable proportion represent in the context of disease and exposure?
The expected reduction in disease if the exposure could be removed
In the context of vaccine efficacy and vaccine effectiveness, when is vaccine efficacy used?
During a clinical trial
What does a vaccine efficacy of 90% indicate?
90% reduction in disease occurrence among the vaccinated group
What does the term 'vaccine effectiveness' refer to?
The typical field conditions during a study
In the context of vaccine effectiveness, what does a 72% reduction in varicella cases among the vaccinated group indicate?
72% reduction from the number of cases you would expect if they had not been vaccinated
What does the calculation of attributable proportion assume about the risk of disease in the exposed group compared to the unexposed group?
The difference in risk can be attributed directly to the exposure
In a study of smoking and lung cancer, what does it mean if about 88% of the lung cancer among smokers may be attributable to their smoking?
88% of lung cancer is directly caused by smoking
What does vaccine efficacy measure among vaccinated persons?
% reduction in risk of disease relative to unvaccinated persons
When studying vaccine efficacy and vaccine effectiveness, what is measured to determine the % reduction?
% reduction in number of cases among vaccinated and unvaccinated persons
In an outbreak of varicella (chickenpox) in Oregon, what does a VE (Vaccine Efficacy) of 72% indicate?
72% reduction from the number of cases you would expect if they had not been vaccinated
What do vaccine efficacy and vaccine effectiveness measure?
Reduction in number of cases among vaccinated persons compared with unvaccinated persons
In calculating attributable proportion, what is assumed about the risk of disease between exposed and unexposed groups?
The difference can be attributed directly to exposure
What does a risk ratio of 1.0 indicate?
Identical risk among the two groups
In the context of public health impact, which measure reflects the burden that an exposure contributes to the frequency of disease in the population?
Attributable proportion
What does an odds ratio compare?
Health outcomes in 2 groups
In a case-control study, what is the measure of choice for quantifying the relationship between exposure and outcome?
Odds ratio
What does a rate ratio greater than 1.0 indicate?
Increased risk for the group in the numerator
What does the attributable proportion represent in the context of disease and exposure?
Burden that an exposure contributes to disease frequency
What is assumed about the risk of disease in the exposed group compared to the unexposed group when calculating attributable proportion?
No difference in risk between the two groups
In a study of smoking and lung cancer, what does it mean if about 88% of lung cancer among smokers may be attributable to their smoking?
Smoking plays a major role in causing lung cancer
What do vaccine efficacy and vaccine effectiveness measure?
The % reduction in disease occurrence
What does a two-by-two table (contingency table) help to analyze?
The relationship between exposure and outcome
In the context of vaccine efficacy and vaccine effectiveness, when is vaccine efficacy used?
In comparing incidence rates between vaccinated and unvaccinated groups
Study Notes
Risk Ratio and Odds Ratio
- Risk ratio compares the risk of disease between exposed and unexposed groups
- Odds ratio compares the odds of being exposed among cases and controls
Characteristics of Persons
- Inherent characteristics, biologic characteristics, and acquired characteristics are examples of confounding variables
Rate Ratio
- Rate ratio compares the rate of disease between exposed and unexposed groups
- A rate ratio greater than 1.0 indicates a higher rate of disease in the exposed group
Two-by-Two Table (Contingency Table)
- Helps to analyze the relationship between an exposure and a particular disease
- Used to calculate measures such as risk ratio, odds ratio, and attributable proportion
Attributable Proportion
- Represents the proportion of disease that can be attributed to an exposure
- Assumes that the risk of disease is greater in the exposed group compared to the unexposed group
- In a study of smoking and lung cancer, an attributable proportion of 88% means that 88% of lung cancer among smokers may be attributed to their smoking
Vaccine Efficacy and Vaccine Effectiveness
- Vaccine efficacy measures the percentage reduction in disease incidence among vaccinated persons
- Vaccine effectiveness measures the percentage reduction in disease incidence in a population
- Vaccine efficacy is used when the analysis is restricted to the vaccinated group
- A vaccine efficacy of 90% indicates that the vaccine is 90% effective in preventing disease among vaccinated persons
- A vaccine effectiveness of 72% indicates that the vaccine is 72% effective in reducing disease incidence in the population
- In an outbreak of varicella (chickenpox) in Oregon, a vaccine efficacy of 72% indicates that the vaccine is 72% effective in preventing disease among vaccinated persons
Public Health Impact
- Attributable proportion reflects the burden that an exposure contributes to the frequency of disease in the population
Test your understanding of measures of association such as risk, odds, and two-by-two tables in the context of biostatistics. This quiz covers the quantification of the relationship between exposure and disease.
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