Epidemiology: Principles, Concepts and Uses · 50 MCQs
NEET PG-style questions. Tap an option: you are marked instantly and every option is explained, including why the wrong ones are wrong.
A student writes: epidemiology is the study of the distribution and determinants of disease-related states in specified populations.
Which component of Last's definition is missing from this statement?
Why B is correct: Last's definition has three components: distribution, determinants, and the application of this study to the control of health problems. The student has written the first two and stopped — the action clause, which makes epidemiology an applied science, is missing.
Ruling out the others:
- A. Frequency is one of the three components of epidemiology, not a clause of Last's definition.
- C. 'In specified populations' is already present in the student's sentence.
- D. Agent identification is part of the determinants, which the student did include.
A district surveillance officer tabulates dengue cases of the last month by week of onset, by block and by age group, without yet testing any hypothesis about why they cluster.
This activity corresponds to which part of the definition of epidemiology?
Why B is correct: Counting cases by time (week), place (block) and person (age group) is the description of distribution — the who, where and when of part ① — i.e. descriptive epidemiology.
Ruling out the others:
- A. Determinants would require testing why the cases cluster; no hypothesis has been tested.
- C. Application means acting on a finding to control the problem; no action has been taken.
- D. Evaluation judges whether an action worked; there has been no action.
Last's definition uses the phrase 'states or events' rather than the word 'diseases'.
Which of the following is the best reason for this wording?
Why A is correct: The phrase deliberately widens the object of study beyond disease to injuries, behaviours such as tobacco use, disability, immunisation coverage and use of health services.
Ruling out the others:
- B. The definition is not tied to any classification system.
- C. The definition concerns populations, not individual diagnoses.
- D. Laboratory confirmation is not a criterion in the definition.
In 1854 a physician plotted cholera deaths on a street map of a London district, found them clustered around one public water pump, and had its handle removed — decades before the organism was known.
Which two parts of the definition of epidemiology does this episode illustrate?
Why A is correct: Snow described the distribution of deaths by place (a spot map) and acted on the population by removing the pump handle (application). The biological determinant — Vibrio cholerae — was unknown to him.
Ruling out the others:
- B. The determinant — the organism and its route — was unknown to him; he acted without it.
- C. The determinant was not identified; the spot map was a description of distribution.
- D. This omits the distribution that was the whole basis of the finding.
The three components of epidemiology are distinguished from the three parts of Last's definition.
Which list gives the three components of epidemiology?
Why A is correct: The three components are disease frequency (measurement as rates and ratios), distribution (time, place, person) and determinants (causes and risk factors). Frequency is the measuring tool; distribution is part ① and determinants part ② of the definition.
Ruling out the others:
- B. That is the epidemiological triad, a model of causation.
- C. That is the classification of epidemiological studies.
- D. Those are the levels of prevention.
Forty cases of jaundice are reported from one lane of a town in a fortnight.
Why does an epidemiologist insist on knowing the size of the population from which the cases arose before interpreting the number?
Why D is correct: Epidemiology studies 'specified populations': a countable denominator turns a count into a rate, and only rates can be compared — forty cases in a lane of 400 and in a city of four million are different problems.
Ruling out the others:
- A. A case definition is based on clinical and laboratory criteria, not on population size.
- B. An attack rate is computed among the population at risk, not among cases — a muddled use of the term.
- C. Incubation period comes from exposure and onset dates, not from population size.
A medical officer manages each of forty jaundice patients correctly and discharges them with advice; a visiting resident instead asks where the families draw water, when the cases began, who is affected and whether the rest of the block shows a rise.
Which statement best describes the difference between the two responses?
Why C is correct: The clinical approach treats each presenting patient; the epidemiological approach asks who, where, when and compared with whom about a defined population, so that the determinant can be found and acted upon.
Ruling out the others:
- A. Nothing the officer did was wrong — it was correct clinical care; the two approaches are complementary.
- B. The resident did not examine or treat patients at all; she asked population questions.
- D. Treating individual cases is not epidemiology; the unit of study differs.
A statistician produces an elegant description of the seasonal pattern of malaria cases in a district and stops there; an epidemiologist uses the same pattern to time an indoor residual spraying round and then measures whether cases fall.
Which clause of the definition of epidemiology separates the epidemiologist's work from the statistician's?
Why A is correct: Both described the distribution in a specified population; only the epidemiologist applied the finding to control and evaluated it — the clause that makes epidemiology an applied science rather than a branch of statistics.
Ruling out the others:
- B. Both the statistician and the epidemiologist described the distribution.
- C. Both worked on the same district population.
- D. Both studied the same event, malaria.
The definition of epidemiology as 'the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems' is attributed to a particular author.
Who is that author?
Why D is correct: The wording is from John M. Last's Dictionary of Epidemiology, the standard modern definition adopted in textbooks.
Ruling out the others:
- A. Snow investigated cholera in 1854; he is a founder, not the author of the definition.
- B. Farr built vital statistics and death registration.
- C. Hill is associated with the criteria for causation and the smoking–lung cancer studies.
Epidemiology is said to have three aims.
Which of the following is NOT one of the three aims of epidemiology?
Why C is correct: Treatment of the individual is the aim of clinical medicine. The three aims of epidemiology are all population-level: describe, identify causes, and provide data for planning, implementation and evaluation.
Ruling out the others:
- A. This is the first aim.
- B. This is the second aim.
- D. This is the third aim.
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