Equations

Question 1

Proportions

Answer 1

simple %; part-over-whole

division of 2 related #

Question 2

Ratios

Answer 2

division of 2 unrelated #

numerator not part of denominator

Question 3

Rate

Answer 3

Proportion % with time incorporated in denominator

Question 4

incidence (risk or attack rate)

Answer 4

of new cases of illness/ # of people at Risk of illness (or in Pop.)

Question 5

incidence rate

Answer 5

of new cases of disease/ person-time at risk for the disease (or in pop.)

ex. 100 people followed for 1 year each; 10 people followed for 10 years each; 1 person followed for 100 years; 25 people followed for 4 years each

Question 6

Prevalence

Answer 6

of existing cases of a disease/ # of persons in population

Question 7

crude morbidity rate

Answer 7

of persons with disease/ # of persons in population

Question 8

crude mortality rate

Answer 8

of deaths (all causes)/ # of persons in population

Question 9

Cause specific morbidity rate

Answer 9

of persons with cause-specific disease/ # of persons in population

Question 10

cause-specific mortality rate

Answer 10

of cause-specific deaths/ # of persons in population

Question 11

cause fatality rate

Answer 11

of cause-specific deaths/ # of cases of disease

Question 12

Cause-specific survival rate

Answer 12

of cause-specific cases alive/ # of cases of disease

Question 13

Proportional mortality rate

Answer 13

of cause-specific deaths/total # of deaths in population

Question 14

Live birth rate (usually per year)

Answer 14

of live births/ 1,000 population

Question 15

Fertility rate (usually per year)

Answer 15

of live births/ 1,000 women of childbearing age (15-44)

Question 16

Neonatal mortality rate (usually per year)

Answer 16

of death in those <28 days of age/1,000 live births

Question 17

Postnatal Mortality rate (usually per year)

Answer 17

of deaths in those > (or equal to) 28 days but <1 year of age/ 1,000 live births

Question 18

infant mortality rate (usually per year)

Answer 18

of deaths in those <1 year of age/ 1,000 live births

Question 19

Maternal mortality ratio

Answer 19

of female deaths related to pregnancy/ 100,000 live births

Question 20

Probability of outcome in (out of) the exposed (Risk in exposed )

Answer 20

A/ (A+B)

Question 21

Probability of outcome in (out of) the non-exposed (Risk in non-exposed)

Answer 21

C/ (C+D)

Question 22

Number needed to treat (NNT) or NUmber needed to harm (NNH)

Answer 22

1/ absolute risk reduction (ARR; in decimal format

Question 23

Risk ratio (RR; aka, Relative risk)

Answer 23

Risk of outcome (in exposed)/ Risk of outcome (in non exposed