1. Disease frequency is primarily measured in epidemiology to:
A. Diagnose diseases
B. Quantify the occurrence of disease in a population
C. Prescribe treatment
D. Develop vaccines
Answer: B
2. Before measuring disease frequency, the most important concept to understand is:
A. Randomization
B. Population at risk
C. Blinding
D. Matching
Answer: B
3. The term population at risk refers to:
A. The total population of a country
B. Individuals who are susceptible to developing a disease
C. Only hospitalized patients
D. Individuals already diagnosed with the disease
Answer: B
4. Population at risk can be defined based on:
A. Demographic factors only
B. Environmental factors only
C. Demographic and environmental factors
D. Genetic factors only
Answer: C
5. Which of the following represents the population at risk for carcinoma of the cervix?
A. All adults
B. Male population
C. Females aged 30–70 years
D. Children below 10 years
Answer: C
6. Which group represents the population at risk for Hepatitis B according to the lecture?
A. Individuals already positive for Hepatitis B
B. Anti-HBc negative individuals
C. All newborns
D. Patients with liver cirrhosis
Answer: B
7. Prevalence is defined as the:
A. Number of deaths in a population
B. Number of new cases only
C. Number of existing (old and new) cases in a defined population at a specified time
D. Number of cured cases
Answer: C
8. Which of the following is included in the numerator of prevalence?
A. New cases only
B. Deaths due to disease
C. Existing (old and new) cases
D. Population at risk
Answer: C
9. The denominator in the prevalence formula is:
A. Existing cases
B. Population at risk
C. Total deaths
D. Incident cases
Answer: B
10. The prevalence formula is:
A. New cases ÷ Total population
B. Existing cases ÷ Population at risk × 10ⁿ
C. Deaths ÷ Cases
D. New cases ÷ Person-time
Answer: B
11. Why is prevalence often multiplied by 10, 100, 1,000, or 100,000?
A. To increase sample size
B. To obtain a more convenient and interpretable number
C. To improve study validity
D. To reduce bias
Answer: B
12. When information on the population at risk is unavailable, researchers may use:
A. Hospital population only
B. The total population as an approximation
C. Only diseased individuals
D. Random samples
Answer: B
13. Prevalence is broadly classified into:
A. Acute and chronic prevalence
B. Point prevalence and period prevalence
C. Primary and secondary prevalence
D. Static and dynamic prevalence
Answer: B
14. Point prevalence measures disease frequency:
A. During a lifetime
B. At a specific point in time
C. Over several years
D. During follow-up only
Answer: B
15. Point prevalence is often compared to a:
A. Motion picture
B. Snapshot
C. Laboratory experiment
D. Clinical trial
Answer: B
16. Point prevalence is best used when data are collected:
A. Continuously over years
B. At one point in time
C. During follow-up only
D. At hospital discharge
Answer: B
17. Which formula correctly represents point prevalence?
A. P = C/N
B. P = I/N
C. P = D/N
D. P = C/T
Answer: A
18. In the point prevalence formula (P = C/N), C represents:
A. Number of cured cases
B. Number of observed cases at a specific time
C. Number of deaths
D. Number of incident cases
Answer: B
19. In the point prevalence formula, N represents:
A. Number of new cases
B. Population size at that time
C. Number of deaths
D. Total person-time
Answer: B
20. A school has 150 children, and 15 have refractive errors during screening. What is the point prevalence?
A. 5%
B. 10%
C. 15%
D. 20%
Answer: B
21. Period prevalence measures disease frequency:
A. At one point in time
B. Over a specified period of time
C. Only at the beginning of a study
D. Only at the end of follow-up
Answer: B
22. Which formula correctly represents period prevalence?
A. PP = C/N
B. PP = (C + I)/N
C. PP = I/PT
D. PP = D/C
Answer: B
23. In the period prevalence formula, I represents:
A. Initial population
B. Incident (new) cases occurring during the study period
C. Immigrated population
D. Infected deaths
Answer: B
24. A population of 150 people has 25 existing cases at the beginning of the year and 15 new cases during the year. What is the period prevalence?
A. 17%
B. 20%
C. 27%
D. 40%
Answer: C
25. Which statement best distinguishes point prevalence from period prevalence?
A. Point prevalence includes only new cases.
B. Period prevalence measures disease over a defined time interval, whereas point prevalence measures disease at a specific point in time.
C. Both measure only incident cases.
D. Both are measures of incidence.
Answer: B
26. Which factor has the greatest influence on the value of prevalence?
A. Number of laboratory tests
B. Number of new cases and duration of illness
C. Hospital bed strength
D. Number of physicians
Answer: B
27. If the duration of a disease is very short, the prevalence generally:
A. Increases
B. Decreases
C. Remains unchanged
D. Becomes equal to incidence
Answer: B
28. Which type of disease is most likely to have a high prevalence because of its long duration?
A. Food poisoning
B. Common cold
C. Diabetes mellitus
D. Influenza
Answer: C
29. A chronic lifelong disease usually results in:
A. Low prevalence
B. High prevalence
C. Zero prevalence
D. High mortality only
Answer: B
30. Which of the following decreases prevalence?
A. Long duration of illness
B. Low cure rate
C. High cure rate
D. Improved detection
Answer: C
31. Which factor may increase prevalence by identifying more existing cases?
A. Poor diagnostic methods
B. Improved diagnostic techniques
C. Increased mortality
D. Shorter disease duration
Answer: B
32. Immigration of patients with a disease into an area generally:
A. Decreases prevalence
B. Increases prevalence
C. Does not affect prevalence
D. Decreases incidence only
Answer: B
33. Emigration of healthy individuals from a population is likely to:
A. Increase prevalence
B. Decrease prevalence
C. Eliminate disease
D. Reduce incidence only
Answer: A
34. Which of the following decreases prevalence?
A. Increased incidence
B. Longer survival
C. High case fatality
D. Immigration of patients
Answer: C
35. Which factor contributes to a reduction in disease prevalence?
A. Long disease duration
B. Low cure rate
C. Decrease in new cases
D. Improved case detection
Answer: C
36. Changes in prevalence should be interpreted carefully because:
A. Prevalence depends on many different factors.
B. Prevalence never changes.
C. Only incidence affects prevalence.
D. Prevalence reflects mortality alone.
Answer: A
37. Which of the following is NOT a use of prevalence data?
A. Assessing healthcare needs
B. Planning health services
C. Measuring burden of chronic diseases
D. Measuring speed of occurrence of new cases
Answer: D
38. Prevalence is particularly useful in studying:
A. Acute poisoning
B. Chronic diseases
C. Epidemics only
D. Outbreak investigations only
Answer: B
39. Incidence refers to the:
A. Number of existing cases
B. Number of deaths
C. Number of new cases occurring during a specified period
D. Number of cured cases
Answer: C
40. Which component is essential while reporting incidence?
A. Age only
B. Time period
C. Gender only
D. Hospital name
Answer: B
41. Incidence measures the:
A. Burden of disease
B. Frequency of old cases
C. Speed or rate of occurrence of new cases
D. Severity of disease
Answer: C
42. Incidence can be expressed as:
A. Absolute numbers only
B. Cumulative incidence only
C. Incidence density only
D. Absolute numbers, cumulative incidence, or incidence density
Answer: D
43. Cumulative incidence is also known as:
A. Prevalence ratio
B. Attack rate
C. Mortality rate
D. Survival rate
Answer: B
44. Which formula correctly represents cumulative incidence (CI)?
A. Existing cases ÷ Population
B. New cases ÷ Population at risk at the beginning × 10ⁿ
C. Deaths ÷ Total population
D. New cases ÷ Person-time
Answer: B
45. Cumulative incidence assumes that:
A. Everyone is lost to follow-up.
B. The entire population at risk is followed throughout the observation period.
C. Only hospitalized patients are included.
D. Disease duration is constant.
Answer: B
46. Which term is most closely related to cumulative incidence?
A. Risk
B. Odds
C. Prevalence
D. Mortality
Answer: A
47. Risk is defined as the:
A. Number of deaths among cases
B. Probability that an individual develops a disease during a specified follow-up period
C. Number of prevalent cases
D. Burden of disease
Answer: B
48. When calculating risk, it is assumed that the individual:
A. Already has the disease
B. Is disease-free at the beginning of follow-up
C. Is hospitalized
D. Has recovered from the disease
Answer: B
49. Which measure corresponds most closely to the concept of risk?
A. Point prevalence
B. Period prevalence
C. Cumulative incidence
D. Incidence density
Answer: C
50. Which statement correctly distinguishes prevalence from incidence?
A. Prevalence measures only new cases.
B. Incidence includes both old and new cases.
C. Prevalence measures existing cases, whereas incidence measures new cases occurring over time.
D. Both measure only chronic diseases.
Answer: C
51. Incidence density is also known as:
A. Attack rate
B. Incidence rate
C. Point prevalence
D. Period prevalence
Answer: B
52. The denominator in the incidence density formula is:
A. Total population
B. Existing cases
C. Total person-time of observation
D. Number of deaths
Answer: C
53. Which formula correctly represents incidence density (ID)?
A. ID = Existing cases ÷ Population at risk
B. ID = New cases ÷ Total person-time of observation × 10ⁿ
C. ID = Deaths ÷ Population
D. ID = Existing cases + New cases ÷ Population
Answer: B
54. Incidence density is preferred because it:
A. Uses only prevalent cases
B. Reflects the exact person-time observed
C. Measures disease severity
D. Eliminates follow-up
Answer: B
55. Which measure is most appropriate when study participants have different follow-up periods?
A. Point prevalence
B. Period prevalence
C. Cumulative incidence
D. Incidence density
Answer: D
56. Which of the following is a major use of incidence data?
A. Measuring disease burden only
B. Describing disease trends over time
C. Calculating case fatality
D. Measuring prevalence only
Answer: B
57. Incidence data are particularly useful for evaluating:
A. Chronic disease burden
B. Primary prevention programmes
C. Hospital bed occupancy
D. Population census
Answer: B
58. Which statement best describes the relationship between incidence and prevalence?
A. They are completely independent.
B. Prevalence depends on incidence and disease duration.
C. Incidence depends on prevalence only.
D. Both measure the same concept.
Answer: B
59. The relationship between prevalence (P), incidence (I), and duration (D) is:
A. P = I + D
B. P = I × D
C. P = I ÷ D
D. P = D ÷ I
Answer: B
60. If incidence remains constant but disease duration increases, prevalence will generally:
A. Decrease
B. Remain unchanged
C. Increase
D. Become zero
Answer: C
61. Which event reduces prevalence by allowing existing cases to leave the population?
A. Cure
B. Death
C. Both cure and death
D. Birth
Answer: C
62. In the “dynamic model” of disease frequency, new cases entering the population represent:
A. Prevalence
B. Mortality
C. Incidence
D. Case fatality
Answer: C
63. In the “dynamic model,” the water remaining in the tank represents:
A. Incidence
B. Prevalence
C. Mortality
D. Attack rate
Answer: B
64. Which disease typically shows high prevalence but low incidence?
A. Common cold
B. Food poisoning
C. Diabetes mellitus
D. Cholera
Answer: C
65. Which disease is an example of low prevalence but high incidence?
A. Diabetes mellitus
B. Hypertension
C. Common cold
D. Rheumatoid arthritis
Answer: C
66. High prevalence with low incidence usually indicates:
A. Short-duration disease
B. Long-duration chronic disease
C. Highly fatal disease
D. Rare disease
Answer: B
67. A disease with high incidence but low prevalence is most likely:
A. Chronic with long survival
B. Acute and short in duration
C. Lifelong and incurable
D. Genetic
Answer: B
68. Case fatality primarily reflects the:
A. Frequency of disease
B. Severity of disease
C. Burden of disease
D. Risk of exposure
Answer: B
69. Case fatality compares:
A. Deaths due to a disease with the total population
B. Deaths due to a disease with the number of cases
C. New cases with the population at risk
D. Existing cases with person-time
Answer: B
70. Case fatality is usually expressed as a:
A. Rate only
B. Ratio or proportion
C. Incidence density
D. Hazard ratio
Answer: B
71. Although commonly called the case fatality rate, it is technically:
A. A prevalence measure
B. A proportion or ratio
C. An incidence measure
D. A mortality rate
Answer: B
72. Mortality differs from case fatality because mortality uses:
A. Cases as the denominator
B. Population as the denominator
C. Person-time only
D. Existing cases only
Answer: B
73. Which statement about mortality is CORRECT?
A. Mortality measures disease severity.
B. Mortality uses the total population as the denominator.
C. Mortality measures only chronic diseases.
D. Mortality is identical to case fatality.
Answer: B
74. Which statement correctly compares mortality and case fatality?
A. Both use the number of cases as the denominator.
B. Mortality reflects disease burden, whereas case fatality reflects disease severity.
C. Both measure prevalence.
D. Both measure incidence.
Answer: B
75. Which statement BEST summarizes disease frequency measures?
A. Prevalence measures existing disease, incidence measures new disease occurrence, and case fatality reflects disease severity.
B. Prevalence and incidence are identical.
C. Incidence measures disease severity.
D. Case fatality measures disease burden in the community.
Answer: A
76. During a cross-sectional survey of 5,000 adults, 250 individuals are found to have hypertension. Which measure is being estimated?
A. Incidence
B. Cumulative incidence
C. Point prevalence
D. Incidence density
Answer: C
77. A cohort of 2,000 disease-free individuals is followed for 5 years, during which 120 develop tuberculosis. Which epidemiological measure is most appropriate?
A. Point prevalence
B. Period prevalence
C. Cumulative incidence
D. Case fatality
Answer: C
78. In a cohort study where participants enter and leave the study at different times, the most appropriate measure of disease occurrence is:
A. Point prevalence
B. Period prevalence
C. Cumulative incidence
D. Incidence density
Answer: D
79. A disease has a constant incidence but its treatment dramatically improves survival without curing patients. Which measure will most likely increase?
A. Incidence
B. Prevalence
C. Case fatality
D. Risk
Answer: B
80. Which situation will most likely increase prevalence without affecting incidence?
A. Increase in new cases
B. Improved survival due to better treatment
C. Higher attack rate
D. Increased exposure to risk factors
Answer: B
81. A new highly sensitive screening test identifies many previously undiagnosed diabetic patients. Which epidemiological measure is expected to increase immediately?
A. Incidence
B. Prevalence
C. Risk
D. Case fatality
Answer: B
82. A disease is rapidly fatal within two days of onset. Which epidemiological pattern is most likely?
A. High prevalence and low incidence
B. High prevalence and high incidence
C. Low prevalence despite high incidence
D. High prevalence despite low incidence
Answer: C
83. Which of the following conditions best explains why diabetes mellitus usually has high prevalence but relatively low incidence?
A. High mortality
B. Long disease duration
C. Short incubation period
D. Rapid recovery
Answer: B
84. An infectious disease outbreak produces 300 new cases within one week among 2,000 susceptible individuals. The MOST appropriate measure is:
A. Point prevalence
B. Period prevalence
C. Attack rate (Cumulative incidence)
D. Incidence density
Answer: C
85. Which measure is most useful for evaluating the effectiveness of a vaccination program?
A. Prevalence
B. Incidence
C. Point prevalence
D. Case fatality
Answer: B
86. If the incidence of a disease remains unchanged but its duration decreases because of improved cure rates, prevalence will:
A. Increase
B. Remain unchanged
C. Decrease
D. Become equal to incidence
Answer: C
87. Which statement best explains why prevalence alone is not a good measure of disease causation?
A. It includes only new cases.
B. It is influenced by both incidence and duration of disease.
C. It excludes chronic diseases.
D. It measures mortality only.
Answer: B
88. Which epidemiological measure directly reflects the speed at which new cases occur?
A. Point prevalence
B. Period prevalence
C. Incidence
D. Case fatality
Answer: C
89. A researcher wants to compare disease occurrence between two populations with different follow-up durations. Which measure is most appropriate?
A. Point prevalence
B. Period prevalence
C. Cumulative incidence
D. Incidence density
Answer: D
90. Which statement regarding risk is CORRECT?
A. Risk can be calculated among individuals already having the disease.
B. Risk corresponds to cumulative incidence.
C. Risk is identical to prevalence.
D. Risk uses person-time as the denominator.
Answer: B
91. A chronic disease has an annual incidence of 5 per 1,000 population and an average duration of 10 years. Assuming a steady state, the approximate prevalence is:
A. 5 per 1,000
B. 10 per 1,000
C. 25 per 1,000
D. 50 per 1,000
Answer: D
Explanation: P ≈ I × D = 5 × 10 = 50 per 1,000
92. Which situation would MOST likely increase incidence without immediately affecting prevalence?
A. Introduction of a new environmental risk factor
B. Improved survival
C. Better treatment
D. Longer disease duration
Answer: A
93. Which of the following best distinguishes incidence density from cumulative incidence?
A. Incidence density includes prevalent cases.
B. Incidence density accounts for person-time of observation.
C. Cumulative incidence measures person-time.
D. Cumulative incidence is used only for chronic diseases.
Answer: B
94. Which measure would BEST estimate the burden of chronic kidney disease in a community?
A. Incidence density
B. Cumulative incidence
C. Point prevalence
D. Attack rate
Answer: C
95. Which epidemiological measure is most appropriate for estimating the probability that an individual will develop a disease during a specified period?
A. Prevalence
B. Incidence density
C. Risk (Cumulative incidence)
D. Case fatality
Answer: C
96. During a five-year follow-up study, several participants migrate out of the study area. Which measure is least affected by these unequal follow-up periods?
A. Point prevalence
B. Period prevalence
C. Cumulative incidence
D. Incidence density
Answer: D
97. Which of the following changes would MOST likely decrease prevalence while incidence remains constant?
A. Increased survival
B. Reduced case fatality
C. Improved cure rate
D. Improved case detection
Answer: C
98. Case fatality is best interpreted as a measure of:
A. Disease occurrence
B. Disease transmission
C. Disease severity
D. Disease burden
Answer: C
99. Which statement is TRUE regarding mortality and case fatality?
A. Both use total population as the denominator.
B. Mortality measures severity of disease.
C. Case fatality uses the number of cases as the denominator, whereas mortality uses the population.
D. Both are measures of incidence.
Answer: C
100. A researcher observes that the prevalence of asthma has doubled over the past decade, while incidence has remained stable. Which is the MOST plausible explanation?
A. Reduced disease duration
B. Improved survival with chronic disease
C. Reduced diagnostic sensitivity
D. Increased case fatality
Answer: B
