Population Health and Epidemiology Flashcards

A study finds that ice cream sales correlate strongly with drowning rates. This is best explained by which concept?

Answer: Confounding by a third variable (season/temperature)

Hot weather (a confounder) increases both ice cream consumption and swimming, producing a spurious correlation between ice cream and drowning.

In an intention-to-treat analysis, participants are analyzed according to:

Answer: Their randomized group assignment regardless of adherence

Intention-to-treat preserves the benefits of randomization by analyzing participants in their originally assigned groups.

The attributable fraction in exposed individuals measures which of the following?

Answer: The proportion of disease among exposed individuals attributable to the exposure

Attributable fraction in exposed = (RR − 1) / RR, representing the proportion of exposed cases due to the exposure.

Which measure is most appropriate for estimating causation in a case-control study?

Answer: Odds ratio

Case-control studies sample on disease status, making incidence impossible to calculate directly; the odds ratio approximates relative risk when disease is rare.

A community-based intervention reduces hypertension prevalence by 5 percentage points (from 30% to 25%). What is the absolute risk reduction?

Answer: 5%

Absolute risk reduction = 30% − 25% = 5 percentage points.

Which of the following study designs is most prone to the ecological fallacy?

Answer: Ecological study

Ecological studies use group-level data; applying group associations to individuals risks the ecological fallacy.

Loss to follow-up in a cohort study is most problematic when:

Answer: Those lost differ from those retained in both exposure and outcome risk

Differential loss to follow-up creates selection bias when dropout is related to both the exposure and the outcome.