,Chapter 1: Introduction
1. A public health researcher wants to estimate the prevalence of obesity in
adults living in Boston. Which term best describes the group of all adults in
Boston?
A. Sample
B. Population
C. Cohort
D. Variable
✅ Correct Answer: B. Population
Rationale: A population is the complete set of individuals or events with a
common characteristic under study. Here, all adults in Boston represent the
population.
Keywords: Population, prevalence, public health research
2. The researcher selects 500 adults from Boston to measure their BMI.
What is this subset called?
A. Population
B. Sample
C. Parameter
D. Variable
✅ Correct Answer: B. Sample
Rationale: A sample is a subset of the population used to draw inferences
about the population. Sampling is essential because studying an entire
population is often impractical.
Keywords: Sample, subset, inference
3. Which type of variable represents categories without a natural order,
such as blood type?
A. Nominal
,B. Ordinal
C. Interval
D. Ratio
✅ Correct Answer: A. Nominal
Rationale: Nominal variables categorize data without implying order.
Blood type (A, B, AB, O) is an example because the categories are distinct
but unordered.
Keywords: Nominal, categorical, variable types
4. A researcher records participants’ education level as “high school,”
“college,” or “graduate school.” What kind of variable is this?
A. Nominal
B. Ordinal
C. Interval
D. Ratio
✅ Correct Answer: B. Ordinal
Rationale: Ordinal variables have categories with a natural order but
unequal differences between categories. Education level shows ranking
(high school < college < graduate).
Keywords: Ordinal, ordered categories, education
5. A variable measured as the number of cigarettes smoked per day is:
A. Continuous
B. Discrete
C. Nominal
D. Ordinal
✅ Correct Answer: B. Discrete
Rationale: Discrete variables take countable values, such as 0, 1, 2
cigarettes. Continuous variables can take any value within a range.
Keywords: Discrete, countable, quantitative
,6. In public health research, which is an example of a parameter?
A. Mean BMI of 200 sampled adults
B. Prevalence of diabetes among all adults in the U.S.
C. Smoking status of 50 participants
D. Gender distribution of a local sample
✅ Correct Answer: B. Prevalence of diabetes among all adults in the U.S.
Rationale: A parameter is a characteristic of an entire population, such as
the true prevalence of diabetes among all adults. Sample statistics estimate
parameters.
Keywords: Parameter, population, prevalence
7. Which type of study design primarily allows researchers to identify
cause-and-effect relationships?
A. Observational
B. Experimental
C. Cross-sectional
D. Descriptive
✅ Correct Answer: B. Experimental
Rationale: Experimental designs involve manipulating an independent
variable and controlling conditions to determine causal effects.
Observational designs cannot establish causation definitively.
Keywords: Experimental design, causation, independent variable
8. A public health student is analyzing mortality rates using secondary data
collected by a health department. What type of data source is this?
A. Primary data
B. Secondary data
C. Nominal data
D. Interval data
,✅ Correct Answer: B. Secondary data
Rationale: Secondary data are data collected by others for purposes other
than the current study, such as public health surveillance databases.
Keywords: Secondary data, mortality rates, public health
9. Which statement best describes the role of biostatistics in public health?
A. It only involves calculating averages.
B. It helps interpret health data to make evidence-based decisions.
C. It is mainly used for laboratory experiments.
D. It replaces the need for clinical judgment.
✅ Correct Answer: B. It helps interpret health data to make evidence-
based decisions.
Rationale: Biostatistics provides methods to summarize, analyze, and
interpret data, supporting informed decisions in public health policies and
interventions.
Keywords: Biostatistics, public health, evidence-based
10. What is the main difference between a qualitative and a quantitative
variable?
A. Qualitative variables are numbers; quantitative variables are categories.
B. Qualitative variables describe characteristics; quantitative variables
measure amounts.
C. Qualitative variables are always discrete; quantitative variables are
always continuous.
D. Qualitative variables require a sample; quantitative variables require a
population.
✅ Correct Answer: B. Qualitative variables describe characteristics;
quantitative variables measure amounts.
Rationale: Qualitative (categorical) variables classify data by attributes,
whereas quantitative variables quantify measurements.
Keywords: Qualitative, quantitative, variable types
, 11. The incidence rate of influenza in a city is calculated per 1,000
population per year. Which type of measure is this?
A. Prevalence
B. Incidence
C. Parameter
D. Sample statistic
✅ Correct Answer: B. Incidence
Rationale: Incidence measures the occurrence of new cases of disease in a
population during a specified period. Prevalence measures all existing
cases at a point in time.
Keywords: Incidence, new cases, population
12. A researcher reports that 60% of a sample of adults are physically
active. This statistic is:
A. A parameter
B. A sample statistic
C. A population variable
D. An experimental outcome
✅ Correct Answer: B. A sample statistic
Rationale: Statistics calculated from a sample estimate characteristics of the
population (parameters). Here, 60% refers to the sample, not the entire
population.
Keywords: Sample statistic, estimate, population inference
13. Why is random sampling important in public health studies?
A. It ensures the population is entirely homogeneous.
B. It minimizes selection bias and allows generalization to the population.
C. It guarantees causation.
D. It eliminates all measurement errors.
1. A public health researcher wants to estimate the prevalence of obesity in
adults living in Boston. Which term best describes the group of all adults in
Boston?
A. Sample
B. Population
C. Cohort
D. Variable
✅ Correct Answer: B. Population
Rationale: A population is the complete set of individuals or events with a
common characteristic under study. Here, all adults in Boston represent the
population.
Keywords: Population, prevalence, public health research
2. The researcher selects 500 adults from Boston to measure their BMI.
What is this subset called?
A. Population
B. Sample
C. Parameter
D. Variable
✅ Correct Answer: B. Sample
Rationale: A sample is a subset of the population used to draw inferences
about the population. Sampling is essential because studying an entire
population is often impractical.
Keywords: Sample, subset, inference
3. Which type of variable represents categories without a natural order,
such as blood type?
A. Nominal
,B. Ordinal
C. Interval
D. Ratio
✅ Correct Answer: A. Nominal
Rationale: Nominal variables categorize data without implying order.
Blood type (A, B, AB, O) is an example because the categories are distinct
but unordered.
Keywords: Nominal, categorical, variable types
4. A researcher records participants’ education level as “high school,”
“college,” or “graduate school.” What kind of variable is this?
A. Nominal
B. Ordinal
C. Interval
D. Ratio
✅ Correct Answer: B. Ordinal
Rationale: Ordinal variables have categories with a natural order but
unequal differences between categories. Education level shows ranking
(high school < college < graduate).
Keywords: Ordinal, ordered categories, education
5. A variable measured as the number of cigarettes smoked per day is:
A. Continuous
B. Discrete
C. Nominal
D. Ordinal
✅ Correct Answer: B. Discrete
Rationale: Discrete variables take countable values, such as 0, 1, 2
cigarettes. Continuous variables can take any value within a range.
Keywords: Discrete, countable, quantitative
,6. In public health research, which is an example of a parameter?
A. Mean BMI of 200 sampled adults
B. Prevalence of diabetes among all adults in the U.S.
C. Smoking status of 50 participants
D. Gender distribution of a local sample
✅ Correct Answer: B. Prevalence of diabetes among all adults in the U.S.
Rationale: A parameter is a characteristic of an entire population, such as
the true prevalence of diabetes among all adults. Sample statistics estimate
parameters.
Keywords: Parameter, population, prevalence
7. Which type of study design primarily allows researchers to identify
cause-and-effect relationships?
A. Observational
B. Experimental
C. Cross-sectional
D. Descriptive
✅ Correct Answer: B. Experimental
Rationale: Experimental designs involve manipulating an independent
variable and controlling conditions to determine causal effects.
Observational designs cannot establish causation definitively.
Keywords: Experimental design, causation, independent variable
8. A public health student is analyzing mortality rates using secondary data
collected by a health department. What type of data source is this?
A. Primary data
B. Secondary data
C. Nominal data
D. Interval data
,✅ Correct Answer: B. Secondary data
Rationale: Secondary data are data collected by others for purposes other
than the current study, such as public health surveillance databases.
Keywords: Secondary data, mortality rates, public health
9. Which statement best describes the role of biostatistics in public health?
A. It only involves calculating averages.
B. It helps interpret health data to make evidence-based decisions.
C. It is mainly used for laboratory experiments.
D. It replaces the need for clinical judgment.
✅ Correct Answer: B. It helps interpret health data to make evidence-
based decisions.
Rationale: Biostatistics provides methods to summarize, analyze, and
interpret data, supporting informed decisions in public health policies and
interventions.
Keywords: Biostatistics, public health, evidence-based
10. What is the main difference between a qualitative and a quantitative
variable?
A. Qualitative variables are numbers; quantitative variables are categories.
B. Qualitative variables describe characteristics; quantitative variables
measure amounts.
C. Qualitative variables are always discrete; quantitative variables are
always continuous.
D. Qualitative variables require a sample; quantitative variables require a
population.
✅ Correct Answer: B. Qualitative variables describe characteristics;
quantitative variables measure amounts.
Rationale: Qualitative (categorical) variables classify data by attributes,
whereas quantitative variables quantify measurements.
Keywords: Qualitative, quantitative, variable types
, 11. The incidence rate of influenza in a city is calculated per 1,000
population per year. Which type of measure is this?
A. Prevalence
B. Incidence
C. Parameter
D. Sample statistic
✅ Correct Answer: B. Incidence
Rationale: Incidence measures the occurrence of new cases of disease in a
population during a specified period. Prevalence measures all existing
cases at a point in time.
Keywords: Incidence, new cases, population
12. A researcher reports that 60% of a sample of adults are physically
active. This statistic is:
A. A parameter
B. A sample statistic
C. A population variable
D. An experimental outcome
✅ Correct Answer: B. A sample statistic
Rationale: Statistics calculated from a sample estimate characteristics of the
population (parameters). Here, 60% refers to the sample, not the entire
population.
Keywords: Sample statistic, estimate, population inference
13. Why is random sampling important in public health studies?
A. It ensures the population is entirely homogeneous.
B. It minimizes selection bias and allows generalization to the population.
C. It guarantees causation.
D. It eliminates all measurement errors.
