This document discusses the key differences between incidence and prevalence in epidemiology. Incidence refers to new or initial cases of a health outcome over a specified time period, while prevalence includes all existing and new cases in the population at a particular point in time. The document provides examples and definitions for prevalence, risk, and rate as measures of disease frequency and occurrence. It also includes a self-evaluation quiz to test understanding of these epidemiological concepts.
Measurement of Epidemiology
Radha Maharjan
MN (WHD)
Contents
5.1 Morbidity
Incidence
Prevalence
Attack Rate
Contents
5.2 Mortality
Crude Death Rate
Case Fatality Rate
Proportional Mortality Rate
Survival Rate
Standardized Death Rate
Contents
5.3 Disability
Disability Adjusted Life Years (DALY)
Quality Adjusted Life Years (QALY)
5.4 Tools of Measurements
Rate
Ratio
Proportion
5.4 Tools of Measurements
Numerator
Numerator refer to the number of times an event (e.g. number of birth) has occurred in a population, during a specified time period.
Denominator
Numerator has little meaning unless it is related to the denominator. The epidemiologist has to choose an appropriate denominator while calculating a rate.
It may be related to:
(I) population
(II) the total events.
Denominator related to the population
Mid year population
Population at risk
Person – time
Sub groups of the population
Denominator related to the Total Events
Mid year population
The population size changes daily due to births, deaths and migration, the mid year population is commonly chosen as a denominator.
The population as on 1st July is mid-year population.
Population at risk
It is important to note that the calculation of measures of disease frequency depends on correct estimates of the numbers of people under consideration.
Ideally, these figures should include only those people who are potentially susceptible to the disease studied.
Population at risk
For instance, men should not be included in denominator for the carcinoma of cervix.
Part of population, which is susceptible to a disease is called the population at risk,
e.g., Occupational injuries occur only among working people so the population at risk is the workforce.
Person – time
In some epidemiological studies (e.g. cohort studies), person may enter into the study at different times.
Consequently, they are under observation for varying time period.
In such case, the denominator is a combination of person and time.
Person – time
The most frequently used person time is person- years.
Some times this may be person- months, person -weeks or man- hours.
For example, if 10 persons were observed in the study for 10 years, person time would be 100 person years of observation.
Person – time
The same figure would be derived if 100 persons were under observation for one year.
These denominators have the advantage of summarizing the experience of persons with different duration of observation or exposure.
Sub groups of the population
The denominator may be subgroups of population
e.g. under-five, female, doctors, etc.
Denominator related to the Total Events
In some instances, the denominator may be related to total events instead of the total population, as in the case of infant mortality rate the denominator is total number of live births.
Definition concept and comparison of ratio, proportion and rate.
Measurement of Epidemiology
Radha Maharjan
MN (WHD)
Contents
5.1 Morbidity
Incidence
Prevalence
Attack Rate
Contents
5.2 Mortality
Crude Death Rate
Case Fatality Rate
Proportional Mortality Rate
Survival Rate
Standardized Death Rate
Contents
5.3 Disability
Disability Adjusted Life Years (DALY)
Quality Adjusted Life Years (QALY)
5.4 Tools of Measurements
Rate
Ratio
Proportion
5.4 Tools of Measurements
Numerator
Numerator refer to the number of times an event (e.g. number of birth) has occurred in a population, during a specified time period.
Denominator
Numerator has little meaning unless it is related to the denominator. The epidemiologist has to choose an appropriate denominator while calculating a rate.
It may be related to:
(I) population
(II) the total events.
Denominator related to the population
Mid year population
Population at risk
Person – time
Sub groups of the population
Denominator related to the Total Events
Mid year population
The population size changes daily due to births, deaths and migration, the mid year population is commonly chosen as a denominator.
The population as on 1st July is mid-year population.
Population at risk
It is important to note that the calculation of measures of disease frequency depends on correct estimates of the numbers of people under consideration.
Ideally, these figures should include only those people who are potentially susceptible to the disease studied.
Population at risk
For instance, men should not be included in denominator for the carcinoma of cervix.
Part of population, which is susceptible to a disease is called the population at risk,
e.g., Occupational injuries occur only among working people so the population at risk is the workforce.
Person – time
In some epidemiological studies (e.g. cohort studies), person may enter into the study at different times.
Consequently, they are under observation for varying time period.
In such case, the denominator is a combination of person and time.
Person – time
The most frequently used person time is person- years.
Some times this may be person- months, person -weeks or man- hours.
For example, if 10 persons were observed in the study for 10 years, person time would be 100 person years of observation.
Person – time
The same figure would be derived if 100 persons were under observation for one year.
These denominators have the advantage of summarizing the experience of persons with different duration of observation or exposure.
Sub groups of the population
The denominator may be subgroups of population
e.g. under-five, female, doctors, etc.
Denominator related to the Total Events
In some instances, the denominator may be related to total events instead of the total population, as in the case of infant mortality rate the denominator is total number of live births.
Definition concept and comparison of ratio, proportion and rate.
Epidemiology basic is a simple way of orientation of the Doctors and health care providers on the basic aspects of epidemiology and research methodology
Sharon L. Bober, Ph.D.
Director, Sexual Health Program
Dana-Farber Cancer Institute
Assistant Professor, Dept. of Psychiatry
Harvard Medical School
Boston, MA
Chapter 3Measures of Morbidity and Mortality Used in .docxketurahhazelhurst
Chapter 3
Measures of Morbidity and
Mortality Used in
Epidemiology
Learning Objectives
• Define and distinguish among ratios,
proportions, and rates
• Explain the term population at risk
• Identify and calculate commonly used
rates for morbidity, mortality, and natality
• State the meanings and applications of
incidence rates and prevalence
Learning Objectives (cont’d)
• Discuss limitations of crude rates and
alternative measures for crude rates
• Apply direct and indirect methods to
adjust rates
• List situations where direct and indirect
adjustment should be used
Overview of Epidemiologic
Measures
Count
• The simplest and most frequently
performed quantitative measure in
epidemiology.
• Refers to the number of cases of a
disease or other health phenomenon
being studied.
Examples of Counts
• Cases of influenza reported in
Westchester County, New York,
during January of a particular year.
• Traffic fatalities in Manhattan in a 24-
hour time period
• College dorm students who had mono
• Foreign-born stomach cancer patients
Ratio
• The value obtained by dividing one
quantity by another.
• Consists of a numerator and a
denominator.
• The most general form has no specified
relationship between numerator and
denominator.
• Rates, proportions, and percentages are
also ratios.
Example of a
Simple Sex Ratio Calculation
• A ratio may be expressed at = X/Y
• Simple sex ratio (data from textbook)
• Of 1,000 motorcycle fatalities, 950 victims
are men and 50 are women.
Number of male cases 950
Number of female cases 50
19:1 male to female= =
Example of a
Demographic Sex Ratio Calculation
• This ratio refers to the number of
males per 100 females. In the U.S.,
the sex ratio in 2010 for the entire
population was 96.7, indicating more
females than males.
Number of male cases 151,781,326
Number of female cases 156,964,212
96.7X 100 = =X 100
Example of a
Sex Ratio at Birth Calculation
• The sex ratio at birth is defined as:
(the number of male births divided by
the number of female births)
multiplied by 1,000.
Number of male births
Number of female births
X 1,000
Definition of Proportion
• A measure that states a count relative
to the size of the group.
• A ratio in which the numerator is part
of the denominator.
• May be expressed as a percentage.
Uses of Proportions
• Can demonstrate the magnitude of a
problem.
• Example: 10 dormitory students
develop hepatitis. How important is
this problem?
– If only 20 students live in the dorm, 50%
are ill.
– If 500 students live in the dorm, 2% are
ill.
Example of a Proportion
• Calculate the proportion of African-
American male deaths among African-
American and white boys aged 5 to 14
years.
Rate
• Definition: a ratio that consists of a
numerator and a denominator and in
which time forms part of the denominat ...
Epidemiology basic is a simple way of orientation of the Doctors and health care providers on the basic aspects of epidemiology and research methodology
Sharon L. Bober, Ph.D.
Director, Sexual Health Program
Dana-Farber Cancer Institute
Assistant Professor, Dept. of Psychiatry
Harvard Medical School
Boston, MA
Chapter 3Measures of Morbidity and Mortality Used in .docxketurahhazelhurst
Chapter 3
Measures of Morbidity and
Mortality Used in
Epidemiology
Learning Objectives
• Define and distinguish among ratios,
proportions, and rates
• Explain the term population at risk
• Identify and calculate commonly used
rates for morbidity, mortality, and natality
• State the meanings and applications of
incidence rates and prevalence
Learning Objectives (cont’d)
• Discuss limitations of crude rates and
alternative measures for crude rates
• Apply direct and indirect methods to
adjust rates
• List situations where direct and indirect
adjustment should be used
Overview of Epidemiologic
Measures
Count
• The simplest and most frequently
performed quantitative measure in
epidemiology.
• Refers to the number of cases of a
disease or other health phenomenon
being studied.
Examples of Counts
• Cases of influenza reported in
Westchester County, New York,
during January of a particular year.
• Traffic fatalities in Manhattan in a 24-
hour time period
• College dorm students who had mono
• Foreign-born stomach cancer patients
Ratio
• The value obtained by dividing one
quantity by another.
• Consists of a numerator and a
denominator.
• The most general form has no specified
relationship between numerator and
denominator.
• Rates, proportions, and percentages are
also ratios.
Example of a
Simple Sex Ratio Calculation
• A ratio may be expressed at = X/Y
• Simple sex ratio (data from textbook)
• Of 1,000 motorcycle fatalities, 950 victims
are men and 50 are women.
Number of male cases 950
Number of female cases 50
19:1 male to female= =
Example of a
Demographic Sex Ratio Calculation
• This ratio refers to the number of
males per 100 females. In the U.S.,
the sex ratio in 2010 for the entire
population was 96.7, indicating more
females than males.
Number of male cases 151,781,326
Number of female cases 156,964,212
96.7X 100 = =X 100
Example of a
Sex Ratio at Birth Calculation
• The sex ratio at birth is defined as:
(the number of male births divided by
the number of female births)
multiplied by 1,000.
Number of male births
Number of female births
X 1,000
Definition of Proportion
• A measure that states a count relative
to the size of the group.
• A ratio in which the numerator is part
of the denominator.
• May be expressed as a percentage.
Uses of Proportions
• Can demonstrate the magnitude of a
problem.
• Example: 10 dormitory students
develop hepatitis. How important is
this problem?
– If only 20 students live in the dorm, 50%
are ill.
– If 500 students live in the dorm, 2% are
ill.
Example of a Proportion
• Calculate the proportion of African-
American male deaths among African-
American and white boys aged 5 to 14
years.
Rate
• Definition: a ratio that consists of a
numerator and a denominator and in
which time forms part of the denominat ...
What are the five critical elements ensuring the program planning success?
1) Mobilizing the community
2) Collecting and organizing data
3) Choosing health priorities
4) Developing a comprehensive intervention plan
5) Evaluating PATCH
The four Multiple Determinants of Chronic Disease?
1) Behavioral determinants
2) Healthcare determinants
3) Environmental determinants
4) Social determinants.
What is Epidemiology?
distribution and determinants of health-related states in specified populations, and the application of this study to the control of health problems
compare between person analyzes and Time analyses?
Person: distribution of a disease or condition varies in the population according to personal characteristics, such as age, race, or gender
Time: surveillance systems monitor the trends in occurrence of chronic disease rates through utilizing the epidemic curve to detect outbreaks
4 elements for Health Believe Model
1) Perceived suscssibility
2) Perceived severity
3) Perceived benefits
4) Perceived barrier
5) Cuss action
6) Self-efficacy
cause of tobacco use?
1) Societal and individual factors
2) Advertising and promotion (tobacco” Safer)
3) Access
4) Social norms
5) Individual psychosocial factors
6) Continued tobacco use
7) Inadequate understanding
8) Lower price
elements of a chronic disease surveillance system:
1) Notifiable Disease Systems
2) statistics vital
3) Sentinel Surveillance
4) Chronic Disease Registries
5) Health Surveys
6) Administrative Data Collection Systems
7) Census Data
Frequency measures of health is an important aspect in the planing of the type of services required in a specific population. This is due to the fact that they are able to indicate the type and level of health problems being faced In that population during a specified period of time.
Medical Technology Tackles New Health Care Demand - Research Report - March 2...pchutichetpong
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According to Chris Mouchabhani, Managing Partner at M Capital Group, “Despite all economic scenarios that one may consider, beyond overall economic shocks, medical technology should remain one of the most promising and robust sectors over the short to medium term and well beyond 2028.”
There is a movement towards home-based care for the elderly, next generation scanning and MRI devices, wearable technology, artificial intelligence incorporation, and online connectivity. Experts also see a focus on predictive, preventive, personalized, participatory, and precision medicine, with rising levels of integration of home care and technological innovation.
The average cost of treatment has been rising across the board, creating additional financial burdens to governments, healthcare providers and insurance companies. According to MCG, cost-per-inpatient-stay in the United States alone rose on average annually by over 13% between 2014 to 2021, leading MedTech to focus research efforts on optimized medical equipment at lower price points, whilst emphasizing portability and ease of use. Namely, 46% of the 1,008 medical technology companies in the 2021 MedTech Innovator (“MTI”) database are focusing on prevention, wellness, detection, or diagnosis, signaling a clear push for preventive care to also tackle costs.
In addition, there has also been a lasting impact on consumer and medical demand for home care, supported by the pandemic. Lockdowns, closure of care facilities, and healthcare systems subjected to capacity pressure, accelerated demand away from traditional inpatient care. Now, outpatient care solutions are driving industry production, with nearly 70% of recent diagnostics start-up companies producing products in areas such as ambulatory clinics, at-home care, and self-administered diagnostics.
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India Clinical Trials Market: Industry Size and Growth Trends [2030] Analyzed...Kumar Satyam
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Growing Prevalence of Lifestyle Diseases
The rising incidence of lifestyle diseases such as diabetes, cardiovascular diseases, and cancer is a major trend driving the clinical trials market in India. These conditions necessitate the development and testing of new treatment methods, creating a robust demand for clinical trials. The increasing burden of these diseases highlights the need for innovative therapies and underscores the importance of India as a key player in global clinical research.
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Alongside the 77th World Health Assembly in Geneva on 28 May 2024, we launched the second version of our Index, allowing us to track progress and give new insights into what needs to be done to keep populations healthier for longer.
The speakers included:
Professor Orazio Schillaci, Minister of Health, Italy
Dr Hans Groth, Chairman of the Board, World Demographic & Ageing Forum
Professor Ilona Kickbusch, Founder and Chair, Global Health Centre, Geneva Graduate Institute and co-chair, World Health Summit Council
Dr Natasha Azzopardi Muscat, Director, Country Health Policies and Systems Division, World Health Organisation EURO
Dr Marta Lomazzi, Executive Manager, World Federation of Public Health Associations
Dr Shyam Bishen, Head, Centre for Health and Healthcare and Member of the Executive Committee, World Economic Forum
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Navigating Challenges: Mental Health, Legislation, and the Prison System in B...Guillermo Rivera
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CHAPTER 1 SEMESTER V - ROLE OF PEADIATRIC NURSE.pdfSachin Sharma
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1. Direct Patient Care:
Objective: Provide comprehensive and compassionate care to infants, children, and adolescents in various healthcare settings (hospitals, clinics, etc.).
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Monitoring vital signs and physical condition.
Administering medications and treatments.
Performing procedures as directed by doctors.
Assisting with daily living activities (bathing, feeding).
Providing emotional support and pain management.
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Objective: Promote healthy behaviors and educate children, families, and communities about preventive healthcare.
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Administering vaccinations.
Providing education on nutrition, hygiene, and development.
Offering breastfeeding and childbirth support.
Counseling families on safety and injury prevention.
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Objective: Collaborate effectively with doctors, social workers, therapists, and other healthcare professionals to ensure coordinated care for children.
Objective: Advocate for the rights and best interests of their patients, especially when children cannot speak for themselves.
This includes tasks like:
Communicating effectively with healthcare teams.
Identifying and addressing potential risks to child welfare.
Educating families about their child's condition and treatment options.
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Objective: Stay up-to-date on the latest advancements in pediatric healthcare through continuing education and research.
Objective: Contribute to improving the quality of care for children by participating in research initiatives.
This includes tasks like:
Attending workshops and conferences on pediatric nursing.
Participating in clinical trials related to child health.
Implementing evidence-based practices into their daily routines.
By fulfilling these objectives, pediatric nurses play a crucial role in ensuring the optimal health and well-being of children throughout all stages of their development.
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2. Purpose
• In this lecture we will focus on two basic
measures of disease frequency incidence and
prevalence.
3. Introduction
• To determine which factors impact health
outcomes at the population level,
epidemiologists employ several different
study designs.
• These designs are used to examine the
relationship between exposures (or
determinants) and health outcomes.
• A health outcome may be a disease,
condition, death, event or a change in health
status or behavior. For example, in addition
to diseases, we may study health events such
as injuries or the occurrence of an “event”
such as preterm birth.
4. Introduction
• Persons who experience the outcome of
interest are commonly referred to as cases.
• One of the first things to consider when
developing a study is whether you will
measure prevalent or incident cases.
5. Prevalent
cases
• All individuals are living with the outcome
of interest within a specified timeframe,
regardless of when that person was
diagnosed or developed the health outcome.
6. Example
• In a study of prevalent cases of diabetes with
a one-year time period, anyone who has
diabetes during the one-year study period
would be counted as a case.
• These prevalent cases would include both
people who have diabetes at the outset of the
study year as well as any who developed
diabetes over the course of the study.
7. Incident
cases
All individuals who change in status from non-
disease to disease – or from one state of a
health outcome to another – over a specific
period of time. In other words, “incidence”
refers to the occurrence of new cases.
8. Example
• In a study of incident cases of diabetes with a
one-year time period, only those who
developed diabetes over the course of the
one-year study period are considered incident
cases.
10. Prevalence
• Prevalence is the proportion of a population
living with a specific health outcome within
a specified time. It is the only measure of
occurrence calculated with prevalent cases.
• To calculate prevalence, the number of
prevalent cases (numerator) is divided by the
total population at risk (denominator.)
• The total population at risk denominator
includes the prevalent cases.
• Prevalence is often reported as a percentage.
11. Prevalence
Prevalence = Prevalent cases / Total
population
• Depending on the type of prevalence being
calculated, the denominator can be either an
average of the population over time or a
single measurement at a specific point of
time.
12. Prevalence
• Prevalence can either be calculated as a point
prevalence or period prevalence.
• A point prevalence is calculated with data
from one specific point in time, while a
period prevalence is calculated over a range
of time.
• Prevalence is directly affected by the
incidence and duration of the health outcome
under study, which makes it a poor choice for
diseases or outcomes with a short duration or
high mortality rate.
13. Example
• Vibrio vulnificus – a disease caused by
consumption of raw shellfish – has a low
incidence and short duration. Therefore, the
few new (incident) cases that arise will
remain prevalent in the population for only a
short time before the cases recover or die.
However, for a disease like diabetes, which
has a higher risk or rate and longer duration,
the prevalence will be higher than the risk or
rate and is a valuable measure of the burden
of disease in the population.
14. Risk
• Like prevalence, risk is also a measure of the
extent of a health outcome in a population.
However, unlike prevalence, risk is the
proportion of an at-risk population that develops
a specific health outcome within a specified
amount of time.
• The numerator for risk is incident cases, and the
denominator includes only those at-risk of
developing the outcome of interest at the
beginning of study follow-up.
15. Risk
• Risk = Incident cases / Population at-risk Risks
are often reported as a scaled value, such as
cases per 1,000; 10,000; or 100,000 population.
16. Example
• If the disease under study is ovarian cancer,
which obviously only affects women, the
denominator should consist only of women
in the population who, at the start of study
observation, do not have ovarian cancer and
can develop ovarian cancer.
17. Rate
• Rate is another measure of health outcome
occurrence calculated with incident cases of
the health outcome. However, the
denominator for a rate is the total amount of
person-time at-risk.
18. Rate
• Person-time is an estimate of the actual time-at-risk
– in years, months, or days – that all participants
contributed to a study.
• In its simplest form, person-time is a sum of each
study participant’s time at risk before experiencing
the outcome of interest or exiting the study. This is a
better estimate of the true at-risk population because
it excludes time for participants who are no longer
eligible to experience the outcome of interest. Thus,
rates are a better reflection of health outcome
occurrence in a dynamic population, where
participants may exit the study or become no longer
at risk.
19. Rate
• The unit for a rate is “cases per person-time.”
• Rates are often reported as a scaled value
with a time unit relevant for the study, such
as cases per 1,000 person-years, 12,000
person-months, or 365,000 person-days.
• Rates are favored if the rapidity with which
new cases of the health outcome or new
events are occurring in the population is of
interest.
20.
21. Rate
• The image of the bathtub below graphically
represents the relationships between
prevalence, risk, and rate. In this analogy,
prevalence is the proportion of the tub (the
total population) filled with any water
(prevalent cases and incident cases). Risk is
the proportion of the tub filled with new,
flowing water (incident cases).
• Rate is a measure of how quickly the water
flows into the tub.
• Prevalent cases only leave the prevalence
pool by either recovery, death, migration out
of the population or loss of study follow-up
via the bathtub drain.
22. Characteristic Incidence Prevalence
What is measured Rapidity of disease
occurrence.
Proportion of population
developing new cases of
disease.
Proportion of
population with disease.
Units Cases/person time
or
Cases/population at- risk
cases/total population
(whether newly
diagnosed cases or cases
developing some time in
the past)
Time of disease diagnosis Newly diagnosed Surviving cases, whether
diagnosed recently of at
any time in the past.
Denominator Number of person-years
(or person-months) free of
the disease of interest.
Number of persons free of
disease at baseline.
Number of persons
present in the
population of interest.
23. Terminology
• Prevalent cases – all individuals living with the
health outcome of interest within a specified
timeframe, regardless of when that person was
diagnosed or developed the health outcome
• Incident cases – all individuals who change in status
from one state of health to another (such as non-
disease to disease) over a specific period of time
• Prevalence – the proportion of a population living
with a specific health outcome within a specified
timeframe
• Risk – the proportion of an at-risk population that
develops a specific health outcome within a
specified amount of time
• Rate – the frequency of incident cases per unit of
person-time
24. Self
Evaluation
Q 1: If we wanted to obtain a measure of the
incidence of breast cancer among women in
North Carolina during 1997, what breast
cancer cases would we count in the numerator?
a. All cases of breast cancer among women in
North Carolina in 1997?
b. Only newly diagnosed cases of breast
cancer among women in North Carolina in
1997?
25. Self
Evaluation
Q 2: Assuming that we begin to measure
incidence on January 1, 1997, which North
Carolina women would be counted for the
denominator of the incidence measure?
a. All women in North Carolina in 1997.
b. Only women in North Carolina without
breast cancer on January 1, 1997.
26. Self
Evaluation
• Q 3: To measure the prevalence of breast
cancer among women in North Carolina for
the year 1997, what breast cancer cases
would we count in the numerator?
a. All breast cancer cases reported to the North
Carolina Cancer Registry in 1997?
b. All breast cancer cases ever reported to the
North Carolina Cancer Registry?
c. All surviving breast cancer cases ever
reported to the North Carolina Cancer
Registry?
27. Self
Evaluation
Q 4: If researchers were studying the risk of a woman
having a baby born preterm in the United States in
2013, what would the at-risk population be? Assume
for this question that a pre-term birth is any birth
before 39 weeks gestation. Choose the one best
answer.
a. All women in the United States in 2013
b. All pregnant women in the United States in 2013
c. The actual number of babies born preterm in the
United States in 2013
d. All babies born in the United States in 2013
e. All pregnant women in the United States whose
due dates would mean that the baby could
potentially be born pre-term in the year 2013
28. Self
Evaluation
Q 5: Now researchers want to study the risk of head
injuries that occur while a person was riding a bicycle, in
the United States between 2000-2013. How would the risk
denominator ideally be calculated? Choose the one best
answer.
a. All people living in the United States in the time period
2000-2013
b. All people who rode a bicycle in the United States in
the time period 2000-2013
c. All people who owned or had access to a bicycle in the
United States in the time period 2000-2013
d. The actual number of documented head injuries due to
bicycle accidents in the United States in the time
period 2000-2013
e. All people who had a head injury in the United States
in the time period 2000-2013
29. Reference
• Alexander LK, Lopes B, Ricchetti-Masterson
K, Yeatts KB. Incident vs Prevalent Cases.
Epidemiologic Research and Information
Center (ERIC) Notebook. Second Edition.
2015.
https://sph.unc.edu/files/2015/07/nciph_ERI
C1.pdf