Epidemiology and Public Health MCQs Set 2
Here are the answers to your public health and epidemiology questions, formatted with bold questions and correct answers, followed by an italicized explanation.
1. Prophylactic administration of vitamin K in breast fed babies is an example of:
a. Health Promotion
b. Treatment
c. Specific protection
d. Rehabilitation
e. Primordial
Correct Answer: c. Specific protection
Explanation: Specific protection is a “Primary Level” of prevention where measures are taken to intercept the causes of disease before they involve the host. Administering Vitamin K is a specific action taken to prevent Vitamin K Deficiency Bleeding (VKDB).
2. In a bulk of hundred children out of whom 28 are immunized 2 of them get measles simultaneously. Subsequently 14 get measles. Assuming the efficacy of the vaccine to be 100%, what is the secondary attack rate?
a. 5%
b. 10%
c. 20%
d. 21.5%
e. 19.4%
Correct Answer: c. 20%
Explanation: Secondary Attack Rate (SAR) is calculated as: (Number of exposed persons developing the disease within the incubation period / Total number of exposed susceptible contacts) × 100. Susceptible children = Total (100) – Immunized (28) – Primary cases (2) = 70. $SAR = (14 / 70) \times 100 = 20\%$.
3. A village has a total of 100 under-five children. The coverage with measles vaccine in this age group is 60% (assuming the efficacy of vaccine to be 100%). Following the occurrence of a measles case in a child after a visit outside, t1wenty-six children developed measles. Th2e secondary attack rate of measles is:
a. 25%
b. 40%
c. 50%
d. 65%
e. 66%
Correct Answer: e. 66%
Explanation: Total children = 100. Immunized = 60. Susceptible = 40. Primary case = 1. Susceptible contacts = 40 – 1 = 39. Secondary cases = 26. $SAR = (26 / 39) \times 100 = 66.6\%$.
4. In an epidemiological study the incidence of disease in females is more than that of males but the prevalence is equal in both. It indicates:34
a. Case fatality is more in female56
b. Mortality in male is highe7r8
c. Disease is of less duration in males9
d. Females harbour disease for longer duration10
e. Males harbour disease for longer du11ration
Correct Answer: a. Case fatality is more in female
Explanation: Prevalence is the product of Incidence and Duration ($P = I \times D$). If Incidence is higher in females but Prevalence is equal to males, the Duration of the disease in females must be shorter. A shorter duration in a high-incidence group often implies a higher case fatality rate (the patients die faster).
5. Which one of the following is the Odds ratio, calculated from the given data? (Diseased: Positive 30, Negative 20; Un-diseased: Positive 20, Negative 30)
a. 0.44
b. 1.5
c. 0.8
d. 2.25
e. 2.00
Correct Answer: d. 2.25
Explanation: Odds Ratio (OR) is calculated as $(a \times d) / (b \times c)$. In this table: $a=30, b=20, c=20, d=30$. $OR = (30 \times 30) / (20 \times 20) = 900 / 400 = 2.25$.
6. A total of 300 newly diagnosed patients with laryngeal cancer are allocated to treatment with either surgical excision alone or surgical excision plus radiation treatment. What is the study design?1213
a. Case series report1415
b. Case-control study1617
c18. Clinical trial19
d. Cohort study20
e. Case repo21rt
Correct Answer: c. Clinical trial
Explanation: When the researcher actively “allocates” or intervenes by assigning participants to different treatment groups to compare outcomes, it is an experimental study design, specifically a Clinical Trial.
7. An analysis of the race of patients who visit an emergency room reveals that 40% are white, 25% are black, 20% are Native American, and 15% are Asian. These data would best be depicted graphically with a:2223
a. Venn diagram2425
b. Cumulative frequency gra26ph27
c. Normal curve28
d. Histogram29
e. Pie c30hart
Correct Answer: e. Pie chart
Explanation: A pie chart is ideal for showing the composition of a whole. It effectively displays qualitative (nominal) data such as race or ethnicity as proportions of a total population.
8. A study was conducted in America to find out the proportion of blacks and white Americans in California. This variable chosen is:
a. Nominal
b. Ordinal
c. Continuous
d. Discreet numerical
e. Dichotomous
Correct Answer: e. Dichotomous
Explanation: A dichotomous variable is a type of nominal variable that has exactly two mutually exclusive categories. In this specific study, the population is divided only into “Black” and “White,” making it dichotomous.
9. A public health physician wants to study the load of hypertension in Rawalpindi district to establish special screening & treatment services. Which design is more useful for this?
a. Cross sectional
b. Case series
c. Cohort
d. Case control
e. Experimental
Correct Answer: a. Cross sectional
Explanation: A cross-sectional study (prevalence study) is used to measure the “load” or burden of a disease in a population at a single point in time, providing the necessary data for planning health services.
10. Japan has a high rate of stomach carcinoma and a low rate of colon carcinoma than the U.S. Which study would you suggest to prove or support the environmental effect on the incidence of these cancers?3132
a. Migrant studies3334
b. Case control3536
c. Incidence3738
d. Case r39eports40
e. Mortality survey41
Correct Answer: a. Migrant studies
Explanation: Migrant studies compare the disease rates of people who move from one environment to another. If Japanese migrants to the U.S. take on the cancer profile of Americans, it strongly suggests environmental/lifestyle causes rather than genetic ones.
11. To give the relevant importance to hypertension control in a health service a researcher wants to study the prevalence of hypertension. He chose a cohort study. The design to assess prevalence is?42
a. Inappropriate43
b. Suitable44
c. Quick d. Feasible45
e. 46Expensive
Correct Answer: a. Inappropriate
Explanation: A cohort study is used to measure Incidence (new cases over time). To measure Prevalence (the total number of existing cases at a specific time), a cross-sectional study is the appropriate design.
12. A researcher wants to study natural history of silicosis in a population of industrial workers. Which design is most useful?
a. Cross sectional
b. Case report
c. Case control
d. Incidence
e. Ecological survey
Correct Answer: d. Incidence
Explanation: The “natural history” of a disease refers to its progression over time. This requires an Incidence (longitudinal/cohort) study to track new developments and stages of the disease in a population.
13. If a researcher wants to study precedence relationship between the exposure and effect, which design should he prefer?
a. Descriptive survey
b. Ecological survey
c. Case series
d. Cross sectional
e. Cohort
Correct Answer: e. Cohort
Explanation: A cohort study is prospective; it begins with an exposure and follows subjects forward in time to see the effect. This clearly establishes “temporality” (that the exposure preceded the disease).
14. Smokers have risk of lung cancer four times more than non smokers. If smoking indicates causal association this characteristic gives:47
a. Specificity48
b. Strength of association49
c. Coherence50
d. Consistency51
e. Temporal seque52nce
Correct Answer: b. Strength of association
Explanation: The “Relative Risk” (in this case, 4 times higher) is a measure of the Strength of Association in Bradford Hill’s criteria for causation. The higher the ratio, the more likely the association is causal.
15. The incidence of gonorrhoea is continuously increasing in a particular locality. An investigator reveals that mostly sex workers are living there. This epidemic may be classified as:5354
a. Common source single exposure5556
b. Common source continuous exposure5758
c. Pr59opagated epidemic60
d. Slow epidemic61
e. modern epidemi62c
Correct Answer: b. Common source continuous exposure
Explanation: In a common source continuous exposure, the source of infection is persistent. Because the sex workers (the source) remain in the locality and continue to transmit the disease to new clients over time, the incidence increases steadily.
16. A public health physician wants to study the load of hypertension in Rawalpindi district to establish special screening & treatment services. Which design is more useful for this?
a. Cross sectional
b. Case series
c. Cohort
d. Case control
e. Experimental
Correct Answer: a. Cross sectional
Explanation: Identical to question 9; cross-sectional studies are the gold standard for assessing disease burden and prevalence in a specific population.
17. In a prospective study of the relationship between oral contraceptive use and development of heart disease, a cohort of 1000 women were followed for 5 years. (Present/Absent: Used OC 245/75, Didn’t use 50/630). What is the incidence rate among those who didn’t use OCs?
a. 630 / (50 + 630)
b. 75 / (245 + 75)
c. 50 / (50 + 630)
d. 245 / (245 + 75)
e. 680/(320+680)
Correct Answer: c. 50 / (50 + 630)
Explanation: The incidence rate in the non-exposed group is calculated as: (Number of new cases in non-exposed / Total number of people in the non-exposed group). Here, 50 women developed the disease out of a total of 680 (50 + 630) who didn’t use OCs.
18. 10 cases of food poisoning reported: 2 mild GI symptoms, 4 moderate dehydration, 2 succumbed. The characteristic of the organism producing the severest form of the disease is:
a. Infectivity
b. Pathogenicity
c. Virulence
d. Communicability
e. Resistibility
Correct Answer: c. Virulence
Explanation: Virulence refers to the degree of pathogenicity or the severity of the disease produced by an organism. It is often measured by the case fatality rate or the proportion of clinical cases that are severe/fatal.
19. The incidence of gonorrhoea is continuously increasing in a particular locality… mostly sex workers are living there. This epidemic is classified as:
a. Common source single exposure
b. Common source continuous exposure
c. Propagated epidemic
d. Slow epidemic
e. modern epidemic
Correct Answer: b. Common source continuous exposure
Explanation: Identical to question 15; the source is constant and ongoing.
20. In Rawalpindi general hospital during December, 10 patients were admitted with meningococcal meningitis. Total inpatients were 800. What is the incidence rate per 1000?
a. 11.5 / 1000
b. 12.5 / 1000
c. 13.0 / 1000
d. 9.0 / 1000
e. 10.5 / 1000
Correct Answer: b. 12.5 / 1000
Explanation: The rate is (Number of cases / Population at risk) × 1000. $(10 / 800) \times 1000 = 0.0125 \times 1000 = 12.5 \text{ per } 1000$.
21. While investigating a point source epidemic… The relative risk of fish is 0.7. It was concluded that fish was not responsible. Why?
a. 0.7
b. 1.2
c. 1.7
d. 3.0
e. 7.0
Correct Answer: a. 0.7
Explanation: A Relative Risk (RR) of 1.0 means there is no association. A RR > 1.0 means increased risk. A RR < 1.0 (like 0.7) means the exposure is actually associated with a lower risk of disease, indicating it is likely not the cause.
22. Among 10 women with cervical cancer, medical records confirm past history of herpes simplex type II in eight. What is the odds of history of HSV II?
a. 8/10
b. 10/8
c. 8/2
d. 2/10
e. 2/8
Correct Answer: c. 8/2
Explanation: Odds are defined as the ratio of the probability of an event occurring to the probability of it not occurring. Here, 8 women had the history and 2 did not. The odds are $8/2$.
23. In an outbreak of cholera in a village of 2,000 population, 20 cases occurred and 5 died. Case fatality rate is:
a. 1%
b. 25%
c. 5%
d. 25% (Repeated option)
e. .0025%
Correct Answer: d. 25%
Explanation: Case Fatality Rate (CFR) = (Number of deaths from a disease / Total number of cases of that disease) × 100. $CFR = (5 / 20) \times 100 = 25\%$.
24. What is the incidence of new cases per 1000 person years in households that had a culture positive case during the first survey?
a. 0.02
b. 0.01
c. 1.0
d. 10
e. 20
Correct Answer: d. 10
Explanation: This is typically a specific statistic derived from classic epidemiological studies on tuberculosis or similar infectious diseases. It refers to the secondary incidence rate in high-risk households.
25. In a population of 1000, measles coverage is 60%, one child goes out of station and comes back with measles from whom 20 more children get measles. Secondary attack rate is:
a. 0.65%
b. 5%
c. 6%
d. 6.5%
e. 7%
Correct Answer: b. 5%
Explanation: Total = 1000. Immunized = 600. Susceptible = 400. Primary case = 1. Susceptible contacts = 400 – 1 = 399. Secondary cases = 20. $SAR = (20 / 399) \times 100 \approx 5\%$.