Stats

Question 1

Calculation of risk ratio (relative risk)

Answer 1

Absolute risk in exposed / absolute risk in non-exposed

Question 2

Calculation of risk difference

Answer 2

Absolute risk in exposed minus absolute risk in non-exposed

Question 3

Calculation of odds ratio

Answer 3

(A x D) / (B x C)

Question 4

When does the odds ratio approximate the risk ratio?

Answer 4

In a rare disease

Question 5

What type of statistical measure does a case control study use?

Answer 5

Odds ratio

Question 6

Definition of sensitivity, and how to calculate it

Answer 6

The percent of true disease correctly identified by screening test
Sensitivity = true positives / (true positives + false negatives)

Question 7

Definition of specificity, and how to calculate it

Answer 7

Percent of a population free of disease correctly identified as not having the disease by the screen test
Specificity = true negatives/ (true negatives + false positives)

Question 8

Definition of positive predictive value, and how to calculate it

Answer 8

The percent of individuals who tested positive that do have true disease
Positive predictive value = true positives/ (true positives + false positives)

Question 9

Definition of negative predictive value, and how to calculate it

Answer 9

The percent of individuals who tested negative that do not have true disease, or the probability of not having true disease when the test is negative
Negative predictive value = true negatives / (true negatives plus false negatives)

Question 10

Calculation of positive likelihood ratio

Answer 10

Sensitivity/(1-specificity)

Question 11

Calculation of negative likelihood ratio

Answer 11

(1-sensitivity)/specificity

Question 12

How to get odds from probability

Answer 12

Odds= probability/(1-probability)

Question 13

How to get probability from odds

Answer 13

Probability= odds /(1+odds)

Question 14

Calculation of prematurity rate

Answer 14

Births <37 weeks gestation/live births x1000

Question 15

Fetal mortality rate calculation

Answer 15

Fetal deaths/(live births+fetal deaths) x1000

Question 16

Calculation of perinatal mortality rate

Answer 16

(Fetal deaths >= 28 weeks gestation + neonatal deaths <7 days) / (live births + Fetal deaths >= 28 weeks gestation)

Question 17

Neonatal mortality rate calculation

Answer 17

Neonatal deaths <28 days /live births x 1000
(Early if within first 7 days and late if after 7 days and before 28)

Question 18

Calculation of postneonatal mortality rate

Answer 18

Postneonatal deaths (28 days to 364 days) / Live births x1000

Question 19

Infant mortality rate calculation

Answer 19

Infant deaths (<=1 year)/ live births x1000

Question 20

Calculation of birth weight specific mortality

Answer 20

Deaths in specific birthweight category/number of births in same birthweight category x 1000