MPH Epidemiology & Biostatistics 3

Question 1

Sensitivity of a diagnostic test refers to:

Accepted Answer

The ability to correctly identify those with the disease

Answer

The ability to correctly identify those without the disease

Answer

The probability a positive test is truly positive

Answer

The proportion of true negatives among all negatives

Question 2

Which type of bias occurs when disease status influences recall of past exposures?

Accepted Answer

Recall bias

Answer

Surveillance bias

Answer

Attrition bias

Answer

Observer bias

Question 3

What does 'attributable risk percent' measure?

Accepted Answer

The proportion of disease in the exposed that is due to the exposure

Answer

The excess risk in the exposed compared to the unexposed

Answer

The percent of total disease in the population attributable to exposure

Answer

The percent reduction in risk after removing exposure

Question 4

A Kaplan-Meier curve is used to:

Accepted Answer

Display survival or event-free probabilities over time

Answer

Compare means between multiple groups

Answer

Estimate odds ratios in case-control studies

Answer

Adjust for multiple confounders simultaneously

Question 5

Effect modification (interaction) in epidemiology means:

Accepted Answer

The effect of an exposure on an outcome differs across strata of a third variable

Answer

Two exposures cause the same outcome through different pathways

Answer

A confounding variable masks the true association

Answer

Random measurement error inflates the association

Question 6

What is the primary advantage of a prospective cohort study over a retrospective cohort study?

Accepted Answer

Exposure data are collected before disease occurs, reducing recall bias

Answer

Lower cost and shorter duration

Answer

Better control of selection bias

Answer

Larger sample sizes are possible