Which term best describes the proportion of a population that has the disease at a specific point in time?

During an outbreak investigation the team wants to formally test whether attendance at a campus event is associated with sickness, without assigning any intervention. Which study type should they choose?

In a case-control study of the game-night illness, investigators found: cases exposed = 60, cases unexposed = 40, controls exposed = 30, controls unexposed = 70. What is the odds ratio (OR) for exposure and illness?

A prospective cohort follows 600 students: 200 exposed at game nights and 400 unexposed. After follow-up, 50 exposed students developed illness and 20 unexposed developed illness. What is the relative risk (RR) of illness for exposed versus unexposed?

Two strata from a case-control investigation produce these data:

Stratum 1: a1=20, b1=5, c1=10, d1=15 (n1=50)

Stratum 2: a2=15, b2=20, c2=25, d2=40 (n2=100).

Calculate the Mantel-Haenszel pooled odds ratio (OR_MH).