NR 503
Study Guide for Final Exam
1. Objectives of epidemiology
a. Understand the aetiology or cause of a disease (risk factors)
b. Find out the extent that a disease or health problem affects a
community or population
c. Determine the natural history or prognosis
d. Evaluate existing and newly developed preventative therapeutic
measures and modes of healthcare delivery
2. Define, compare, calculate, and interpret Measures of Morbidity
a. Incidence rate: measurement of the number of new individuals who
contract a disease during a particular period of time
i. Calculation: Number of new cases of disease or injury during
specified period DIVIDED BY Size of population at start of
period
b. Attack rate: Same as risk, proportion of individuals in a population
(initially free of disease) who develop the disease within a specified
time interval.
i. Calculation: Total number of new cases DIVIDED BY The total
population
c. Prevalence: measurement of all individuals affected by the disease at
a particular time
i. Calculation: Number of new cases of disease or injury during
specified period DIVIDED BY Time each person was observed,
totaled for all persons
d. These rates are used to measure disease occurrence and make
comparisons between population groups. They are commonly used
measures that help our understanding of the distribution of disease in
a given population.
3. Understand why incidence data are important for measuring risk.
a. Incidence is important for measuring risk because it tells you the rate
at which new people are contracting the disease
4. Define, compare, calculate, and interpret Measures of Mortality
a. Mortality: a measure of the frequency of occurrence of death in a
defined population during a specified interval. Morbidity and
mortality measures are often the same mathematically; it's just a
matter of what you choose to measure, illness or death.
i. Calculation: Deaths occurring during a given time period
DIVIDED BY Size of the population among which the deaths
occurred TIMES 10n
, b. Cause-specific mortality rate: The mortality rate from a specified
cause for a population.
i. Calculation: The number of deaths attributed to a specific cause
DIVIDED BY The size of the population at the midpoint of the
time period
c. Annual mortality rate: The rate of death in a one-year period.
i. Calculation: Deaths occurring within the one-year period
DIVIDED BY Size of population in which the deaths occured
d. Case-fatality: the proportion of deaths within a designated population
of "cases" (people with a medical condition) over the course of the
disease
i. Calculation: he number of deaths from a specified disease over
a defined period of time DIVIDED BY The number of
individuals diagnosed with the disease during that time TIMES
100 (final answer should be percentage)
e. Proportionate mortality: the proportion of deaths in a particular
population over a specified period of time, attributable to different
causes
i. Calculation: Number of deaths within a population due to a
specific disease or cause DIVIDED BY the total number of
deaths in the population during a time period such as a year.
5. Assess the Validity and Reliability of Diagnostic and Screening Tests
a. Define, compare and calculate measures of validity, including
sensitivity and specificity.
i. Sensitivity identifies the proportion of individuals who truly
DO have the disease AND are given a positive test result. I find
it helpful to remember: sensiTivity = sensitive to the Truth (i.e.
do have disease + do have positive result)
1. We want to know what proportion of individuals who
have the disease (a+c) were given a positive test result
(a), therefore…
a. Sensitivity = a/(a+c)
ii. Specificity identifies the proportion of individuals who truly
DO NOT have the disease AND were given the correct negative
test result. I find it helpful to remember: specificity = speciFies
the False (i.e. do not have disease and do not have positive test
result
1. This time we want to know what proportion of people
who do not have the disease (b+d) were given the correct
negative test result (d), therefore…
a. Specificity = d/(b+d).
Study Guide for Final Exam
1. Objectives of epidemiology
a. Understand the aetiology or cause of a disease (risk factors)
b. Find out the extent that a disease or health problem affects a
community or population
c. Determine the natural history or prognosis
d. Evaluate existing and newly developed preventative therapeutic
measures and modes of healthcare delivery
2. Define, compare, calculate, and interpret Measures of Morbidity
a. Incidence rate: measurement of the number of new individuals who
contract a disease during a particular period of time
i. Calculation: Number of new cases of disease or injury during
specified period DIVIDED BY Size of population at start of
period
b. Attack rate: Same as risk, proportion of individuals in a population
(initially free of disease) who develop the disease within a specified
time interval.
i. Calculation: Total number of new cases DIVIDED BY The total
population
c. Prevalence: measurement of all individuals affected by the disease at
a particular time
i. Calculation: Number of new cases of disease or injury during
specified period DIVIDED BY Time each person was observed,
totaled for all persons
d. These rates are used to measure disease occurrence and make
comparisons between population groups. They are commonly used
measures that help our understanding of the distribution of disease in
a given population.
3. Understand why incidence data are important for measuring risk.
a. Incidence is important for measuring risk because it tells you the rate
at which new people are contracting the disease
4. Define, compare, calculate, and interpret Measures of Mortality
a. Mortality: a measure of the frequency of occurrence of death in a
defined population during a specified interval. Morbidity and
mortality measures are often the same mathematically; it's just a
matter of what you choose to measure, illness or death.
i. Calculation: Deaths occurring during a given time period
DIVIDED BY Size of the population among which the deaths
occurred TIMES 10n
, b. Cause-specific mortality rate: The mortality rate from a specified
cause for a population.
i. Calculation: The number of deaths attributed to a specific cause
DIVIDED BY The size of the population at the midpoint of the
time period
c. Annual mortality rate: The rate of death in a one-year period.
i. Calculation: Deaths occurring within the one-year period
DIVIDED BY Size of population in which the deaths occured
d. Case-fatality: the proportion of deaths within a designated population
of "cases" (people with a medical condition) over the course of the
disease
i. Calculation: he number of deaths from a specified disease over
a defined period of time DIVIDED BY The number of
individuals diagnosed with the disease during that time TIMES
100 (final answer should be percentage)
e. Proportionate mortality: the proportion of deaths in a particular
population over a specified period of time, attributable to different
causes
i. Calculation: Number of deaths within a population due to a
specific disease or cause DIVIDED BY the total number of
deaths in the population during a time period such as a year.
5. Assess the Validity and Reliability of Diagnostic and Screening Tests
a. Define, compare and calculate measures of validity, including
sensitivity and specificity.
i. Sensitivity identifies the proportion of individuals who truly
DO have the disease AND are given a positive test result. I find
it helpful to remember: sensiTivity = sensitive to the Truth (i.e.
do have disease + do have positive result)
1. We want to know what proportion of individuals who
have the disease (a+c) were given a positive test result
(a), therefore…
a. Sensitivity = a/(a+c)
ii. Specificity identifies the proportion of individuals who truly
DO NOT have the disease AND were given the correct negative
test result. I find it helpful to remember: specificity = speciFies
the False (i.e. do not have disease and do not have positive test
result
1. This time we want to know what proportion of people
who do not have the disease (b+d) were given the correct
negative test result (d), therefore…
a. Specificity = d/(b+d).
