30 Questions
What is the formula to calculate relative risk?
Incidence in exposed / Incidence in non exposed
In the context of relative risk, what does a value of 1 indicate?
There is no association between risk in exposed and non-exposed
How is risk interpreted when relative risk (RR) is above 1?
Risk is increased by (RR - 1)X100%
Why can't relative risk be calculated in a case-control study?
Due to lack of incident data
What does a relative risk value less than 1 indicate?
Risk in exposed is decreased compared to non-exposed
If incidence among smokers was given as 84 per 3,000 instead of 28 per 1,000, what would be the relative risk?
3.5
What is the formula to calculate Incidence Rate?
Number of New Cases / Population at Risk
What does Incidence measure?
Number of new cases of a disease in a population during a specific period
How much did the proportion of the population with HIV change from 2020 to 2021?
0.1%
What is used to determine whether a certain disease is associated with a certain exposure?
Relative risk
How is Relative Risk defined?
Ratio of the probability of an event in exposed group to non-exposed group
What does Prevalence measure?
Proportion of individuals with a disease at a specific time
In a case-control study, the odds ratio is a good estimate of the relative risk when:
The disease being studied is rare
What does an odds ratio of 1 indicate in relation to exposure and disease?
No relationship between exposure and disease
How is the odds ratio calculated in a case-control study?
$\frac{a \times d}{b \times c}$
When can the odds ratio also be used in cohort studies to estimate the relative risk?
When the disease under study is infrequent
How is risk affected when the odds ratio is greater than 1?
Risk increases by the amount of (OR - 1)%
In which hybrid study design is a case-control study conducted based on a defined cohort?
Nested Case-Cohort study
What was the relative risk for developing breast cancer among women exposed to DDT compared to those not exposed?
2.15
What was the percentage of women who developed breast cancer in the entire cohort?
1.60%
Why were all 89,949 baseline blood samples not analyzed?
Funding constraints
What would be the cost to analyze all 89,949 blood samples if it cost $20 per sample?
$1.8 million
Which study design could be applied to overcome the cost issue of analyzing all blood samples in this scenario?
Nested Case-Cohort study
What was the risk ratio among women who developed breast cancer based on DDT exposure status?
=1.8
In a case-control study, what is the purpose of analyzing blood samples from non-diseased women?
To calculate the odds ratio for the association between exposure and disease
If the odds ratio (OR) for breast cancer in DDT-exposed women is 1.89, what can be inferred about the association between DDT exposure and breast cancer?
DDT exposure increases the risk of breast cancer
In a cross-sectional study, what measure is used to determine the association between exposure and disease?
Prevalence ratio
If the prevalence ratio is less than 1.0, what does it indicate about the association between exposure and disease?
The prevalence of disease is lower in the exposed group
In the given data, what is the total cost of analyzing blood samples for the case-control study?
$86,320
Based on the given data, what is the prevalence of breast cancer among the non-exposed women?
0.85
Test your knowledge on calculating HIV incidence and prevalence based on new cases and population at risk. Understand how to interpret the results and compare proportions between different time periods.
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