Public health science USMLE step 1 Practice Questions and Answers
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Course
USMLE
Institution
USMLE
Public health science USMLE step 1
Practice Questions and Answers
What number is in the denominator for the RATE of divorce? -
Answer️️ -Per 100 marriages
What number is in the denominator for the RATE of infant mortality? -
Answer️️ -Per 1000 live births
What is the typical RATE give...
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
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
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?
What type of study design is this?
How would you analyze data from this study?
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