One child in a kindergarten room had a slight fever and did not eat lunch. Otherwise, the child seemed OK. Three days later, several children were absent from kindergarten. Which best describes what happened?

Correct Answer: B

Rationale: Frequently, the communicable period begins before symptoms are present. The communicable period, or communicability, follows latency and begins with shedding of the agent. The incubation period is the time from invasion to the time when disease symptoms first appear. Thus, even if parents kept their children away from the child with the fever, this could possibly be ineffective because their children may have already been exposed before the child exhibited symptoms. It is unlikely that the children suddenly changed schools. Although, there may be many reasons why parents keep their children home from school, in this situation there is a specific reason that can be identified.

Correct Answer: C

Rationale: Rates are calculated by the number of people with the problem over the number exposed to the problem. In this case, 650 persons out of the 1000 at the banquet complained of illness. Although this rate could be presented as an attack rate of 65%, 6.5% is incorrect.

Correct Answer: B

Rationale: Prospective studies monitor a group of individuals to determine if and when disease occurs. A cross-sectional study examines relationships between potential causal factors and disease at a specific time. A retrospective study compares individuals with a particular condition or disease with those who do not have the disease. A true experiment involves both an experimental group who receives an intervention and a control group who does not receive an intervention.

Correct Answer: A

Rationale: In epidemiology, 'exposure' is any factor (e.g., smoking, diet, BMI) that may influence health, positively or negatively (A), making it true. B assumes all exposures increase risk, which isn’t always true (e.g., exercise reduces risk). C is false; dietary intake is an exposure despite being a choice. D is false; BMI is a single exposure linked to multiple outcomes.

Correct Answer: D

Rationale: Epidemiological studies include descriptive (A), observational (B), and interventional (C) types. Qualitative study (D) is a social science method, not typically epidemiological.