Diagnostic tests

Question 1

probability that when the

disease is present, the test is positive.

Answer 1

Sensitivity (true positive rate)

Question 2

probability that when the

disease is absent, the test is negative

Answer 2

Specificity (true negative rate)

Question 3

Probability that a person who has a positive test

result actually has the disease.

Answer 3

Positive predictive

value

Question 4

Probability that a person with a negative test

result actually does not have the disease

Answer 4

Negative predictive

value

Question 5

Probability that a person who has a positive test

result actually donot has the disease.

Answer 5

reciprocal of PPV

Question 6

Probability that a person who has a negative test

result actually has the disease.

Answer 6

reciprocal of NPV

Question 7

Median survival rate is calculated in _______ or _______

Answer 7

Cohort study or clinical trial

Question 8

Intention to treat:

Answer 8

Once randomized, always analyzed

Question 9

Opposite of intention to treat is

Answer 9

as treated/ per protocol

if patient switches therapy they are counted as members of new group during analysis

Question 10

Difference between descriptive and analytical study?

Answer 10

descriptive study is useful in generating the hypothesis but not used in drawing conclusions.

Question 11

Examples of descriptive study:

Answer 11

Individial level: 
1. case report
2. case series
3. cross-sectional study
Population level:
Correlational (ecological)

Question 12

Nested case control studies:

Answer 12

start with cohort studies → followed over time → those who develop an outcome of interest become cases for a case control study

Question 13

Advantage of Intention to treat:

Answer 13

helps to reduce selection bias (selective non-compliance) ; preserves randomization

Question 14

Relative risk differs depending on ________

Answer 14

number of cases you choose

OR donot change with number of cases

Question 15

OR = RR when

Answer 15

prevalence is <10%

rare disease assumption

Question 16

Odds of an event occurring is defined as

Answer 16

probability of that event happening divided by probability of that event not happening

Question 17

______ is the measure of strength of an association between an exposure and an outcome

Answer 17

Odds ratio

Question 18

Effect of ↑ accuracy of diagnostic testing on incidence and prevalence

Answer 18

both increase

Question 19

Effect of Research on incidence and prevalence

Answer 19

no effect on either

Question 20

Precision (reliability)

The absence of _______ in a test.

Answer 20

random variation

Question 21

Accuracy (validity)

The absence of _________ in a test.

Answer 21

systematic error or bias

Question 22

Out of precision and accuracy ______ is not affected by sample size

Answer 22

accuracy

Question 23

how much variability
exists in a set of values, around the mean of
these values

shown by?

Answer 23

Standard deviation =

Question 24

p-value means:

p-value represents:

Answer 24

the probability of obtaining that result purely
by chance

the probability that null hypothesis is true (no association)

Question 25

paired T-test

Answer 25

compares 2 means from same individual followed over time (baseline BMI vs BMI after treatment)