Frequency measures

Question 1

Each row is called a ____

contains information about one individual

Answer 1

“record” or “observation.”

Question 2

Each column is called a ____

contains information about one characteristic such as race or date of birth

Answer 2

“variable.”

Question 3

In epidemiology, many nominal variables have only two possible categories:
alive or dead
case or control
exposed or unexposed …… Such variables are called ___

Answer 3

dichotomous variables

Question 4

The frequency measures we use with dichotomous variables are ___

Answer 4

ratios, proportions, and rates = (x/y) x 10^n

Question 5

In a ___ , the values of x and y may be completely independent, or x may be included in y.

Answer 5

ratio

Question 6

A ___ , the second type of frequency measure used with dichotomous variables, is a ratio in which x is included in y

Answer 6

proportion

Question 7

The third type of frequency measure used with dichotomous variables, ___ , is often a proportion, with an added dimension

Answer 7

rate = (# of cases or events during a given time period) / (population at risk during the same time period) x 10^n

It measures the occurrence of an event in a population over time.

Question 8

The ___ rate expresses the probability or risk of illness in a population over a period of time.

Answer 8

incidence rate = (new cases occurring during a given period of time) / (pop. at risk during the same time period) x 10^n

Question 9

___ rate, is the proportion of persons in a population who have a particular disease or attribute at a specified point in time or over a specified period of time.

Answer 9

prevalence (presence of a disease) = (all new & pre-existing cases during a given time period) / (population during the same period of time) x 10^n

prevalence (of an attribute) = (persons having a particular attribute during a given time period) / (population during the same period of time) x 10^n

Question 10

How much of a particular disease is present in a population at a single point in time.

Answer 10

Point prevalence

Question 11

How much of a particular disease is present in a population over a longer period.

Answer 11

Period prevalence

Question 12

Attack rate formula ?

Answer 12

A.R = (# of new cases among the population during the period) / (pop. at risk at the beginning of the period) x 100

Question 13

Secondary attack rate formula?

Answer 13

S.A.R = (# of cases among contacts of primary cases during the period) / (total # of contacts) x 10^n

Question 14

A ___ ___, or ___ ___, compares the risk of some health-related event such as disease or death in two groups.

Answer 14

risk ratio or or relative risk = (risk for grp. of primary interest) / (risk for comparison grp.) x 1

Question 15

risk ratio of 1.0 indicates?

Answer 15

A risk ratio of 1.0 indicates identical risk in the two groups.

Question 16

risk ratio greater than and less than 1.0 indicates?

Answer 16

A risk ratio greater than 1.0 indicates an increased risk for the numerator group, while a risk ratio less than 1.0 indicates a decreased risk for the numerator group.

“How much more likely”

Question 17

Odds ratio formula?

Answer 17

Odds ratio (cross-product ratio) looks at increased odds of getting a disease with exposure to a risk factor versus non exposure to that factor .

OD = ad/bc

Question 18

When the health outcome is uncommon, the ___ ___ provides a good approximation of the relative risk.

Answer 18

odds ratio

Question 19

A ___ ___ is a measure of the frequency of occurrence of death in a defined population during a specified interval.

Answer 19

mortality rate = (deaths occurring during a given time period) / (size of pop. among which deaths occurred) x 10^n

Question 20

case-fatality rate formula?

Answer 20

C-F rate= (# of cause specific deaths among the incident cases) / (# of incident cases) x 10^n

Case-fatality rate is a proportion and requires that the deaths in the numerator be limited to the cases in the denominator.

Question 21

Specific rate formula?

Answer 21

SR = (all events in specified subpopulation) / (specified subpopulation) x multiplier

Question 22

Adjusted rates?

Answer 22

• Rates calculated to minimize demographic differences between populations being compared.
• Adjustment improves the validity of the comparison.

eg.
- The rate of alcoholism and alcohol abuse is found to be higher among workers in an automobile assembly plant compared with same-age workers at a textile mill in the same city.
- Adjustment for gender differences is warranted.