Relative Risk and Odds Ratio Quiz

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Questions and Answers

What does the odds ratio commonly measure in case-control studies?

The effectiveness of treatment interventions

The risk of disease in a cohort study

The association between exposure and disease (correct)

The prevalence of a disease in the population

In the context of odd ratios, which scenario would indicate a positive association between exposure and disease?

An odds ratio of 1

An odds ratio of 0

An odds ratio greater than 1 (correct)

An odds ratio less than 1

Which statement is true about the interpretation of odds ratios?

An odds ratio of 1 indicates no association between variables (correct)

An odds ratio of 2 means the exposure decreases the disease risk by half

An odds ratio of 0.5 suggests a twofold increased risk

An odds ratio can only be calculated in cohort studies

What is a primary limitation of using odds ratios in case-control studies?

They do not provide information on actual risks Signup and view all the answers

What role does the investigator play in the context of a case-control study when using odds ratios?

To identify and compare exposure levels between cases and controls Signup and view all the answers

In which type of study are odds ratios most commonly used?

Case-control studies Signup and view all the answers

Which statement about odds ratios is true?

They can also be applied in cohort and cross-sectional studies. Signup and view all the answers

What is a necessary condition for applying odds ratios in non-case-control studies?

Some modifications and/or assumptions may be necessary. Signup and view all the answers

Which of the following study designs would least benefit from the use of odds ratios?

Experimental studies Signup and view all the answers

Why might odds ratios need modifications in certain study designs?

To align with the assumptions of the specific design. Signup and view all the answers

What does a relative risk (RR) greater than 1 indicate?

A positive association between exposure and outcome Signup and view all the answers

How is relative risk calculated using the 2x2 table?

Risk in exposed / risk in non-exposed Signup and view all the answers

What does a relative risk value of 1 suggest about smokers compared to non-smokers concerning CHD?

There is no difference in CHD incidence between smokers and non-smokers Signup and view all the answers

If the incidence of stroke is 40 per 1000 in hypertensives and 20 per 1000 in normotensives, what is the relative risk for stroke among hypertensives compared to normotensives?

2.0 Signup and view all the answers

What conclusion can be drawn from a relative risk of 1.6 when comparing smokers to non-smokers for CHD?

Smokers are 1.6 times more likely to develop CHD than non-smokers Signup and view all the answers

What does an odds ratio (OR) of 3.8 indicate in the context of borderline personality disorder and depression?

There is a strong positive association with the outcome. Signup and view all the answers

In a study comparing smokers and non-smokers, if the odds ratio (OR) is calculated to be 1.63, what can be concluded?

Smokers have a higher risk of CHD compared to non-smokers. Signup and view all the answers

How is the odds ratio (OR) calculated for an outcome in a prospective study?

The ratio of odds of outcome in the exposed group to odds in the unexposed group. Signup and view all the answers

What does it mean when the odds ratio (OR) equals 1?

There is no association between exposure and outcome. Signup and view all the answers

Which of the following is true regarding odds ratios (OR) and their interpretation?

An OR equal to 1 suggests no association. Signup and view all the answers

What is the primary reason for using Odds Ratio (OR) in case-control studies?

It estimates relative risk when disease occurrence is low. Signup and view all the answers

How is the Odds Ratio (OR) calculated in a study?

By calculating the ratio of odds of exposure in cases to the odds of exposure in controls. Signup and view all the answers

In the given study about suicide attempts, what is the calculated Odds Ratio (OR) based on the provided data?

4.73 Signup and view all the answers

Which of the following statements is true regarding the relationship between Odds Ratio (OR) and Relative Risk (RR)?

RR can be estimated using OR when the disease risk is low. Signup and view all the answers

What advantage does OR have over other measures in statistical analyses?

It is symmetric and can be interpreted in both directions. Signup and view all the answers

What does a higher Odds Ratio (OR) suggest about the association between exposure and outcome?

Strong association between exposure and outcome. Signup and view all the answers

In a case-control study, why might the calculation of Relative Risk (RR) be directly infeasible?

It requires information about the general population at risk. Signup and view all the answers

How is the Relative Risk (RR) calculated from the given data of suicide attempts and sexual abuse history?

By dividing the rate of attempts in abused by the rate in non-abused. Signup and view all the answers

Study Notes

Relative Risk

Relative Risk (RR) is the ratio of the probability of developing a disease if a risk factor is present to the probability of developing the disease if it's absent.
A 2x2 Table is used to calculate RR:
- Rows represent exposure (Yes or No)
- Columns represent disease (Yes or No)
- RR is calculated as (a / (a+b)) / (c / (c+d)) where a, b , c and d are the values in the cells of the 2x2 table.
RR > 1 indicates a positive association between exposure and outcome.
RR = 1 indicates no association between exposure and outcome.
RR <1 indicates a negative association between exposure and outcome.
RR tells us about the strength of association, but not the magnitude of absolute risk (incidence).

Odds Ratio

Odds Ratio (OR) is the ratio of the odds of an event occurring in one group to the odds of it occurring in another group.
OR is commonly used in case-control studies but can be used in other study designs.
OR > 1 indicates a positive association between exposure and outcome.
OR = 1 indicates no association between exposure and outcome.
OR < 1 indicates a negative association between exposure and outcome.
The odds of an event are the probability of the event happening divided by the probability of it not happening expressed as a ratio.
OR is calculated as (a/c) / (b/d) where a,b,c and d are the values in the cells of a 2x2 table.
OR is used as an estimate of RR when the risk of disease is low.

Advantages of Odds Ratio

Suitable for case-control studies.
Identical in both directions.
Forms the basis of logistic regression analyses.

Example of RR and OR Calculation

In a study where smokers were found to have a higher rate of CHD (Coronary Heart Disease), RR was calculated as 28.0 / 17.4 = 1.6
This means that smokers are 1.6 times more likely to develop CHD than non-smokers.
OR in this example was calculated as 28.8/17.7 = 1.63, demonstrating a similar relationship to RR.

OR & RR Differences

OR and RR are not always equal, and the difference depends on the prevalence of the outcome.
When the outcome is rare, OR is a good approximation of RR.
When the outcome is more common, OR overestimates RR.
In a case-control study, RR can't be calculated directly, so OR is used as an estimate.

Example of OR and RR Calculation with Suicide Attempts

In a study of suicide attempts, Participants were divided into those with a history of sexual abuse and those without.
The OR of suicide attempts was calculated as 14/9 / 49/149 = 4.73.
The RR of suicide attempts was calculated as 14/23 / 49/198 = 2.46.
The Difference in the OR and RR is that OR focuses on the odds of the outcome within exposed and unexposed groups, while RR focuses on the overall risk within the exposed and unexposed groups.
The OR in this example is higher than the RR because the outcome (suicide attempt) is relatively rare.

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Description

Test your knowledge on the concepts of Relative Risk (RR) and Odds Ratio (OR). This quiz covers the definitions, calculations, and interpretations associated with these important epidemiological measures. Enhance your understanding of how these ratios can inform public health decisions.