Class 1: Descriptive Study Designs

Question 1

Source Population

Answer 1

A group of people with at least one common characteristic (person, place, time, event/exposure)

Question 2

Fixed population

Answer 2

Defined that an event that happens once; permanent membership

Question 3

Dynamic population

Answer 3

Defined by state or condition; transient membership

Question 4

Sample

Answer 4

a subset of the population; ideally selected at random and is representative of the population

Question 5

Exposure (x)

Answer 5

measurable characteristics that differ across individuals and might affect/be associated with health

Question 6

Examples of Exposures

Answer 6

demographics, behaviors, environmental factors, policies, health conditions

Question 7

Health Outcomes (y)

Answer 7

Any measurable disease, disability, injury, infection, syndrome, symptom, biological or subclinical marker, or positive health state

Question 8

Association

Answer 8

a statistical relationship vs causation which implies that exposure produces health effects

Question 9

Causation

Answer 9

The exposure produces the effect

Question 10

Things needed to demonstrate causation

Answer 10

1. association
2. correct time order
3. direction of effect (exposure results in health outcome)

Question 11

Exposures/Risk Factors/ Determinants

Answer 11

put individuals at higher risk for an outcome

Question 12

Modifiable Exposures/Risk Factors/ Determinants

Answer 12

behaviors, housing, education, gender identity

Question 13

Non-modifiable Exposures/Risk Factors/ Determinants

Answer 13

age, sex at birth, race/ethnicity

Question 14

Surrogate markers Exposures/Risk Factors/ Determinants

Answer 14

for ill defined/unknown/hard to measure exposure

Question 15

Descriptive Study Design

Answer 15

description of disease patters, hypothesis generation

Question 16

Types of Descriptive Studies

Answer 16

case reports, case-series, cross-sectional, ecologic

Question 17

Analytic Design Studies

Answer 17

Compare groups to test hypothesis and evaluate interventions

Question 18

Types of Analytic Studies

Answer 18

Observational, comparison studies, evaluations

Question 19

Observational and Comparison Studies

Answer 19

case-control, cohort studies

Question 20

Evaluation of intervention

Answer 20

clinical trials

Question 21

Case Report

Answer 21

description of a single individual’s experience with a health outcome

Question 22

Case Series

Answer 22

description of a group of individuals’ experiences with health outcomes

Question 23

Strengths of case reports/series

Answer 23

-relatively quick and inexpensive
-often conducted on available data
-recognized and describe new/emerging health problems
-generate hypotheses based on similarities among group
-insight into disease mechanisms

Question 24

Limitations of case reports/series

Answer 24

-no formal comparison groups
-cannot infer temporal sequence

Question 25

Ecologic Studies

Answer 25

based on exposure and health outcome at a point in time for more than individuals (counties, states, countries)

Question 26

Unique Feature of Ecologic Studies

Answer 26

unit of measurement is NOT individuals; the data are averages among different populations

Question 27

Strengths of Ecological Studies

Answer 27

-relatively quick and inexpensive -often conducted on available data -good for early stage of knowledge -wider range of exposures -may wish to study ecologic relationships -only population level data (e.g. good for laws)

Question 28

Limitations of Ecologic Studies

Answer 28

-ecologic fallacy: an exposure to cause an effect in an individual, the exposure and effect should occur in the same person -can't attribute population data to an individual -little to no control for confounding factors

Question 29

Cross-Sectional Studies

Answer 29

individuals defined according to current exposure and health out come at a single point in time can measure prevalence of exposure and outcome at that time

Question 30

Strengths of a Cross-Sectional study

Answer 30

-relatively quick and inexpensive -often conducted on available data -useful for early stage of knowledge -useful for public health planning

Question 31

Limitations of Cross-Sectional Studies

Answer 31

-temporal sequence is often unclear -prevalent cases of long duration may bias results

Question 32

Continuous Variable

Answer 32

assumes any value between minimum and maximum (infinite) e.g. blood pressure, viral load

Question 33

Summary of Continuous variables

Answer 33

-sample mean or median, and standard deviation or interquartile range

Question 34

Ordinal variables

Answer 34

more than two ranked responses (1,2,3)

Question 35

Summary of Ordinal Variables

Answer 35

frequencies and percentages

Question 36

Categorical Variables

Answer 36

grouped and unordered (gender, religion)

Question 37

Summary of Categorical Variables

Answer 37

frequencies and percentages

Question 38

Dichotomous Variables

Answer 38

2 response options

Question 39

Summary of Dichotomous Variables

Answer 39

frequencies and percentages

Question 40

Discrete

Answer 40

variables that assume only a finite number of values (dichotomous, ordinal, categorical)