Lecture 5A, part 1

Question 1

What is the goal of study designs?

Answer 1

To examine the relationship between exposure and dz (or determinant and outcome) with validity and precision while using a minimum of resources

Question 2

Steps in the scientific method

Answer 2

Observe and describe health phenomena
Formulate a hypothesis to explain the phenomena
Test the hypothesis in a research study
Replicate the hypothesis test in additional studies

Question 3

On what does the selection of a design depend?

Answer 3

The research question
Concerns about validity and efficiency
Practical and ethical considerations

Question 4

Hierarchy of research design (from top to bottom)

Answer 4

Meta-analyses
Systematic reviews
Experimental trials (RCTS)
Cohort studies and case-control studies
Cross-sectional and ecological studies
Case studies or case reports

Question 5

Types of descriptive studies

Answer 5

Case reports/case studies
Cross-sectional studies
Ecological/correlational studies

Question 6

Types of analytic studies

Answer 6

Experimental studies
-Field trials, community trials
-Randomized controlled clinical trials, pragmatic trials
Non-experimental studies
-Cohort
-Case-control

Question 7

How are case reports/case studies useful?

Answer 7

ID’ing new dzs

Question 8

Who is usually the focus of case reports/studies?

Answer 8

A single pt or small cluster of pts

Question 9

What do case reports/studies describe?

Answer 9

An unusual or novel outcome

Question 10

Purpose of a case report/case study

Answer 10

Help form hypotheses for additional study
-Unexpected associations
-Possible pathogenesis of dz

Question 11

Purpose of cross-sectional studies

Answer 11

Examine the relationship between dzs (or health outcomes) and RFs as they exist in a defined pop at one particular point in time
-“Snapshot”

Question 12

How are cross-sectional studies measured?

Answer 12

Dz prevalence in relation to exposure prevalence

Question 13

How are pops selected in cross-sectional studies?

Answer 13

Without regard to exposure or dz status

Question 14

What do cross-sectional studies include?

Answer 14

Most large-scale surveys of the general pop

Question 15

Examples of large-scale surveys that do cross-sectional studies

Answer 15

NHANES
BRFSS
NSFG

Question 16

Strengths of cross-sectional studies

Answer 16

Results can be highly generalizable (especially when based on well-selected sample of the general population)
Low cost

Question 17

Limitations of cross-sectional studies

Answer 17

More likely to ID prevalent cases of long duration
Temporal sequence between exposure and dz cannot always be inferred

Question 18

When can temporal sequence between exposure and dz be inferred in cross-sectional studies?

Answer 18

If timing of exps is ascertained relative to measurement of prevalence

Question 19

When is temporal sequence not an issue in cross-sectional sutdies?

Answer 19

When exposure is an unalterable characteristic (genetic trait)

Question 20

Purpose of ecological studies

Answer 20

Examines rates of dz by aggregated pops

Question 21

What are the units of analysis in ecological studies?

Answer 21

Pops or groups rather than individuals

Question 22

What is a property of the pop in ecological studies?

Answer 22

Exposure status

Question 23

Types of ecological studies

Answer 23

Completely ecologic
Partially ecologic- some but not all variables are ecologic
Multilevel

Question 24

What variables are present in completely ecological studies?

Answer 24

All variables (outcome, exposure, covariates)

Question 25

Description of multilevel ecological studies

Answer 25

Analyses may simultaneously include multilevel and ecological variables on the same construct (also called multi-level modeling, hierarchical regression, or mixed effects modeling)