HSCI 130 FINAL REVIEW QUESTIONS
what is prevalence - Answers - the proportion of indivduals with the disease at a given
time
what is the formula for prevalence - Answers - number of cases / total population
how is prevalence reported - Answers - as a percentage
What is period prevalence - Answers - proportion of individuals in a population with
disease at a specific point in time
what is the formula for point prevalence - Answers - number of cases of disease / total
population at the specific time
how is point prevalence reported - Answers - as a percentage
what is period prevalence - Answers - the proportion of individuals in a population with
the disease at any given point with a given time period
what is the formula for period prevalence - Answers - number of cases of disease / total
population within that time period
how is period prevalence reported - Answers - as a percentage
what is cumulative incidence - Answers - the proportion of people who become
diseased during a specific time period
what is the formula for cumulative incidence - Answers - number of new cases of
disease / number of people at risk at the beginning of the period
how is cumulative incidence reported - Answers - as a percentage
what is incidence rate - Answers - the rate of development of a disease in a population
what is the formula for incidence rate - Answers - number of ew cases of disease /
person time at risk
how is incidence rate reported - Answers - case per person time
in this example: a study decided to research a group of 1000 newborn infants (some of
which had serious birth defects) for 2 years. within the 1st year of life, 20 of the infants
died. At the end of the study period, another 90 infants died. what is the outcome of
intrest? - Answers - infant mortality
, in this example: a study decided to research a group of 1000 newborn infants (some of
which had serious birth defects) for 2 years. within the 1st year of life, 20 of the infants
died. At the end of the study period, another 90 infants died. how many indivdiuals are
at risk? - Answers - 1000 newborn infants
in this example: a study decided to research a group of 1000 newborn infants (some of
which had serious birth defects) for 2 years. within the 1st year of life, 20 of the infants
died. At the end of the study period, another 90 infants died. calculate the cumulative
incidence for the whole study period? - Answers - (number of new cases of disease / by
number of people at risk at beginning of the period)
- 20 + = 0.11 * 100 = 11%
what is the formula for sensitivity - Answers - TP/(TP+FN)
what does it mean if sensitivity = 1 - Answers - all cases are TP and there are no FN
why do we want to improve sensitivity? - Answers - to decrease false negatives
list three reason why we want to improve sensitivity? - Answers - to decrease false
negatives
a. people will get sick if they don't get treatment
b. these people are still infectious, so they will still spread disease
c. socio-economic consequences of disease/illness for the person and their families
what is the formula for specificity - Answers - TN / (TN + FP)
what does it mean if specificity = 1 - Answers - all cases are TN and no FP
why do we want to improve specificity? - Answers - we want to improve specificity
because it will decrease false positives
list three reason why we want to improve specificity? - Answers - we want to improve
specificity because it will decrease false positives
a. stigma
b. antibiotic resistance
c. efficient use of resources/drugs on people who need them
example: there are 13000 people in a population, prevalence of disease Z is 17%. 4500
people test negative, but 500 of them actually have the disease. calculate sensitivity +
specificity + create a table. - Answers - calculate prevalence: case/total population =
17%
- cases /13000 = 0.17
rearrange the equation > cases = 13000 * 0.17 = 2210
sensitivity = TP / TP + FN
= 1710/1710 + 500 = 0.77 * 100 = 77%
specificity = TN/TN + FP
what is prevalence - Answers - the proportion of indivduals with the disease at a given
time
what is the formula for prevalence - Answers - number of cases / total population
how is prevalence reported - Answers - as a percentage
What is period prevalence - Answers - proportion of individuals in a population with
disease at a specific point in time
what is the formula for point prevalence - Answers - number of cases of disease / total
population at the specific time
how is point prevalence reported - Answers - as a percentage
what is period prevalence - Answers - the proportion of individuals in a population with
the disease at any given point with a given time period
what is the formula for period prevalence - Answers - number of cases of disease / total
population within that time period
how is period prevalence reported - Answers - as a percentage
what is cumulative incidence - Answers - the proportion of people who become
diseased during a specific time period
what is the formula for cumulative incidence - Answers - number of new cases of
disease / number of people at risk at the beginning of the period
how is cumulative incidence reported - Answers - as a percentage
what is incidence rate - Answers - the rate of development of a disease in a population
what is the formula for incidence rate - Answers - number of ew cases of disease /
person time at risk
how is incidence rate reported - Answers - case per person time
in this example: a study decided to research a group of 1000 newborn infants (some of
which had serious birth defects) for 2 years. within the 1st year of life, 20 of the infants
died. At the end of the study period, another 90 infants died. what is the outcome of
intrest? - Answers - infant mortality
, in this example: a study decided to research a group of 1000 newborn infants (some of
which had serious birth defects) for 2 years. within the 1st year of life, 20 of the infants
died. At the end of the study period, another 90 infants died. how many indivdiuals are
at risk? - Answers - 1000 newborn infants
in this example: a study decided to research a group of 1000 newborn infants (some of
which had serious birth defects) for 2 years. within the 1st year of life, 20 of the infants
died. At the end of the study period, another 90 infants died. calculate the cumulative
incidence for the whole study period? - Answers - (number of new cases of disease / by
number of people at risk at beginning of the period)
- 20 + = 0.11 * 100 = 11%
what is the formula for sensitivity - Answers - TP/(TP+FN)
what does it mean if sensitivity = 1 - Answers - all cases are TP and there are no FN
why do we want to improve sensitivity? - Answers - to decrease false negatives
list three reason why we want to improve sensitivity? - Answers - to decrease false
negatives
a. people will get sick if they don't get treatment
b. these people are still infectious, so they will still spread disease
c. socio-economic consequences of disease/illness for the person and their families
what is the formula for specificity - Answers - TN / (TN + FP)
what does it mean if specificity = 1 - Answers - all cases are TN and no FP
why do we want to improve specificity? - Answers - we want to improve specificity
because it will decrease false positives
list three reason why we want to improve specificity? - Answers - we want to improve
specificity because it will decrease false positives
a. stigma
b. antibiotic resistance
c. efficient use of resources/drugs on people who need them
example: there are 13000 people in a population, prevalence of disease Z is 17%. 4500
people test negative, but 500 of them actually have the disease. calculate sensitivity +
specificity + create a table. - Answers - calculate prevalence: case/total population =
17%
- cases /13000 = 0.17
rearrange the equation > cases = 13000 * 0.17 = 2210
sensitivity = TP / TP + FN
= 1710/1710 + 500 = 0.77 * 100 = 77%
specificity = TN/TN + FP
