UPSC CMS PSM - General Epidemiology & Biostatistics

In a closed cohort, cumulative incidence is calculated as:

Consider the following statements:

1. In the context of the question, “All existing cases divided by total population” is the most appropriate conclusion.
2. Cumulative incidence is a risk or proportion over a specified period. Incidence density instead uses person-time in the denominator.

Which of the statements given above is/are correct?

Which measure is most directly estimated in a case-control study?

Consider the following statements:

1. Case-control sampling begins with outcome status, so risks are not measured directly. The exposure odds ratio estimates the incidence rate ratio and approximates the risk ratio when disease is rare.
2. In the context of the question, “Odds ratio” is the most appropriate conclusion.
3. In the context of the question, “Cumulative incidence” is the most appropriate conclusion.

Which of the statements given above is/are correct?

A district epidemiologist is interpreting surveillance and research data before recommending action.

Sensitivity is the probability that a test is positive among people who:

Select the single best answer.

Specificity is the probability that a test is negative among people who:

Consider the following statements:

1. Specificity equals true negatives divided by all non-diseased persons. A highly specific test has few false positives.
2. In the context of the question, “Truly have the disease” is the most appropriate conclusion.

Which of the statements given above is/are correct?

When disease prevalence increases while test sensitivity and specificity remain fixed, positive predictive value generally:

Consider the following statements:

1. In the context of the question, “Decreases” is the most appropriate conclusion.
2. With higher pre-test probability, a positive result is more likely to be a true positive. Negative predictive value generally falls as prevalence rises.

Which of the statements given above is/are correct?