©EMILLECT 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED
FIRST PUBLISH OCTOBER 2024
Public health science USMLE step 1 Exam
Practice Questions and Answers
What number is in the denominator for the RATE of divorce? - ANSWER✔✔-Per 100 marriages
What number is in the denominator for the RATE of infant mortality? - ANSWER✔✔-Per 1000 live births
What is the typical RATE given in epidemiology for most cases? - ANSWER✔✔-Per 100,000.
What are most disease rates in the US for most all diseases? - ANSWER✔✔-Less than 50 per 100,000....
Almost ALL are below 100 per 100,000
What is an INCIDENCE rate? - ANSWER✔✔-The rate of NEW cases in a population divided by people at
risk to be a case
What is a PREVALENCE rate? - ANSWER✔✔-The rate of ALL cases in a population divided by people at
risk to be a case.
How do you remember was an incidence rate is? - ANSWER✔✔-IN-cidence is the rate of new IN-coming
cases
Page 1/71
, ©EMILLECT 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED
FIRST PUBLISH OCTOBER 2024
What type of rates should be associated with Incidence? - ANSWER✔✔-Attack rate---you shrink the
denominator as per the exposure.
Create a difference 'attack rate' for every food that was eaten in a restaurant, saw, and the one with the
highest rate is the culprit. (Acute conditions)
What two prevalences are associated with prevalence rate? - ANSWER✔✔-Point and Period prevalence
What is point prevalence? - ANSWER✔✔-A particular INSTANCE in time....Who has the disease over who
is at risk.
What is period prevalence? - ANSWER✔✔-Period is for a larger period of time, who has it over this
period over who is at risk
Mortality data is by definition what type of date? - ANSWER✔✔-Incidence data....the number of newly
dead
What is the general relationship between prevalence and incidence? - ANSWER✔✔-Prevalence =
incidence x duration....
If either incidence or duration increase, so does prevalence.
What is a CRUDE rate? - ANSWER✔✔-A rate that is generalized to an entire population, ie death rate in
the US in 2000
Page 2/71
, ©EMILLECT 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED
FIRST PUBLISH OCTOBER 2024
What is a SPECIFIC rate? - ANSWER✔✔-One that has been modified to have some sort of qualifier, ie
male death rate in 2000... This is GENDER SPECIFIC
What is a CASE fatality rate? - ANSWER✔✔-The number of deaths from a specific cause (heart disease)
divided by the number of patients with that disease.
What is the Proportionate mortality rate? - ANSWER✔✔-Deaths from a cause (heart disease) divided by
all deaths.
Sensitivity detects what?? - ANSWER✔✔-DISEASE! The calculation deals with diseased people. They
actually HAVE the disease.... So it is true positives divided by the rest, True positives over (TP and the
false negatives)
Specificity detects what?? - ANSWER✔✔-HEALTHY people!! True negatives over all people without the
disease (TN+ FP)
What does PPV detect? - ANSWER✔✔-The value of a positive test result and of course is given by the
TRUE's divided by everything in the row. True positives divided by all positives, TP AND FP
What does NPV detect - ANSWER✔✔-The value of a negative test result, given by the TRUE negatives
divided by all the negatigves, TN and FN
How do you calculate the ACCURACY of a test? - ANSWER✔✔-TP + TN over EVERYTHING, TP FP TN and
FN
Page 3/71
, ©EMILLECT 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED
FIRST PUBLISH OCTOBER 2024
As prevalence increases what happens to positive and negative predictive values? - ANSWER✔✔-PPV
goes up. More people have the disease, thus a + test result is more believable.
NPV goes down. More people have the disease, fewer people are without it so a negative is less likely.
There are NO direct changes on a screening test based on increased or decreased incidence.... -
ANSWER✔✔-Dur.
What is the relationship between pretest probabilities of sensitivity and sensitivity WRT prevalence? -
ANSWER✔✔-NONE...Pretest values are constant and are a measure of the test itself, and will never
change.
What point of the double hump diagram gives you the FEWEST FALSES or the highest accuracy for a test?
- ANSWER✔✔-The point where the two curves cross...To move either direction gives you a few fewer
falses in one category but a whole bunch more falses in another direction.
What is the FIRST thing you need to do when constructing a 2x2 table for the USMLE? - ANSWER✔✔-Pick
a total population number and anchor is with PREVALENCE before plugging in numbers. Prevalence is the
number of people in the population with disease, so for 100 people and prevalence of 20 % is 20 with
disease 80 without....Then plug in the corresponding Sensitivities and Specificities.
What are the four study design questions asked on USMLE questions? - ANSWER✔✔-What type of bias is
there, if any?
How would you fix the bias, if any?
Page 4/71
FIRST PUBLISH OCTOBER 2024
Public health science USMLE step 1 Exam
Practice Questions and Answers
What number is in the denominator for the RATE of divorce? - ANSWER✔✔-Per 100 marriages
What number is in the denominator for the RATE of infant mortality? - ANSWER✔✔-Per 1000 live births
What is the typical RATE given in epidemiology for most cases? - ANSWER✔✔-Per 100,000.
What are most disease rates in the US for most all diseases? - ANSWER✔✔-Less than 50 per 100,000....
Almost ALL are below 100 per 100,000
What is an INCIDENCE rate? - ANSWER✔✔-The rate of NEW cases in a population divided by people at
risk to be a case
What is a PREVALENCE rate? - ANSWER✔✔-The rate of ALL cases in a population divided by people at
risk to be a case.
How do you remember was an incidence rate is? - ANSWER✔✔-IN-cidence is the rate of new IN-coming
cases
Page 1/71
, ©EMILLECT 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED
FIRST PUBLISH OCTOBER 2024
What type of rates should be associated with Incidence? - ANSWER✔✔-Attack rate---you shrink the
denominator as per the exposure.
Create a difference 'attack rate' for every food that was eaten in a restaurant, saw, and the one with the
highest rate is the culprit. (Acute conditions)
What two prevalences are associated with prevalence rate? - ANSWER✔✔-Point and Period prevalence
What is point prevalence? - ANSWER✔✔-A particular INSTANCE in time....Who has the disease over who
is at risk.
What is period prevalence? - ANSWER✔✔-Period is for a larger period of time, who has it over this
period over who is at risk
Mortality data is by definition what type of date? - ANSWER✔✔-Incidence data....the number of newly
dead
What is the general relationship between prevalence and incidence? - ANSWER✔✔-Prevalence =
incidence x duration....
If either incidence or duration increase, so does prevalence.
What is a CRUDE rate? - ANSWER✔✔-A rate that is generalized to an entire population, ie death rate in
the US in 2000
Page 2/71
, ©EMILLECT 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED
FIRST PUBLISH OCTOBER 2024
What is a SPECIFIC rate? - ANSWER✔✔-One that has been modified to have some sort of qualifier, ie
male death rate in 2000... This is GENDER SPECIFIC
What is a CASE fatality rate? - ANSWER✔✔-The number of deaths from a specific cause (heart disease)
divided by the number of patients with that disease.
What is the Proportionate mortality rate? - ANSWER✔✔-Deaths from a cause (heart disease) divided by
all deaths.
Sensitivity detects what?? - ANSWER✔✔-DISEASE! The calculation deals with diseased people. They
actually HAVE the disease.... So it is true positives divided by the rest, True positives over (TP and the
false negatives)
Specificity detects what?? - ANSWER✔✔-HEALTHY people!! True negatives over all people without the
disease (TN+ FP)
What does PPV detect? - ANSWER✔✔-The value of a positive test result and of course is given by the
TRUE's divided by everything in the row. True positives divided by all positives, TP AND FP
What does NPV detect - ANSWER✔✔-The value of a negative test result, given by the TRUE negatives
divided by all the negatigves, TN and FN
How do you calculate the ACCURACY of a test? - ANSWER✔✔-TP + TN over EVERYTHING, TP FP TN and
FN
Page 3/71
, ©EMILLECT 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED
FIRST PUBLISH OCTOBER 2024
As prevalence increases what happens to positive and negative predictive values? - ANSWER✔✔-PPV
goes up. More people have the disease, thus a + test result is more believable.
NPV goes down. More people have the disease, fewer people are without it so a negative is less likely.
There are NO direct changes on a screening test based on increased or decreased incidence.... -
ANSWER✔✔-Dur.
What is the relationship between pretest probabilities of sensitivity and sensitivity WRT prevalence? -
ANSWER✔✔-NONE...Pretest values are constant and are a measure of the test itself, and will never
change.
What point of the double hump diagram gives you the FEWEST FALSES or the highest accuracy for a test?
- ANSWER✔✔-The point where the two curves cross...To move either direction gives you a few fewer
falses in one category but a whole bunch more falses in another direction.
What is the FIRST thing you need to do when constructing a 2x2 table for the USMLE? - ANSWER✔✔-Pick
a total population number and anchor is with PREVALENCE before plugging in numbers. Prevalence is the
number of people in the population with disease, so for 100 people and prevalence of 20 % is 20 with
disease 80 without....Then plug in the corresponding Sensitivities and Specificities.
What are the four study design questions asked on USMLE questions? - ANSWER✔✔-What type of bias is
there, if any?
How would you fix the bias, if any?
Page 4/71
