lecture 4: study designs

Question 1

observe the outcomes without intervening to affect them

Answer 1

observational study

Question 2

The researcher manipulates the exposure (usually a drug or treatment) to compare it to the standard of care

Answer 2

Experimental studies

Question 3

types of observational studies

Answer 3

cohort
case control
cross-section

Question 4

Subjects are selected based their exposure status

Answer 4

Cohort studies

Question 5

compares disease prevalence in the exposed and unexposed

Answer 5

Prospective cohort

Question 6

begin with the exposure of interest and probe back for exposure information

Answer 6

Retrospective cohort

Question 7

disadvantages of cohort studies

Answer 7

expensive
Inefficient for rare diseases
long follow up
Diagnostic trends

Question 8

Subjects are selected based on their disease status

Answer 8

Case-Control Studies

Question 9

Cases and controls should be different only on their past exposure

Answer 9

Case-Control Studies

Question 10

Can demonstrate risk indicators and not risk factors due the retrospective nature of the study design

Answer 10

Case-Control Studies

Question 11

The exposure has to be assessed retrospectively and the proportions of cases and controls who are exposed are unknown at the beginning of the study

Answer 11

Case-Control Studies

Question 12

must have had an equal chance of being exposed case-control studies

Answer 12

cases and controls

Question 13

Efficient for rare diseases

Answer 13

Case-coontrol studies

Question 14

Inefficient for rare diseases

Answer 14

cohort studies

Question 15

allow for the evaluation of multiple exposures that may increase risk for a specific disease

Answer 15

case-control

Question 16

Cannot directly compute incidence of disease in exposed and non-exposed persons

Answer 16

case-control studies

Question 17

Not optimal for rare exposures

Answer 17

case-control studies

Question 18

selection of subjects based on neither exposure or disease status

Answer 18

Cross-sectional Studies

Question 19

Most basic study design

Answer 19

Cross-sectional Studies

Question 20

Subject selected without regards to exposure or disease status

Answer 20

Cross-sectional Studies

Question 21

point-in-time” or “snapshots” information

Answer 21

Cross-sectional Studies

Question 22

Does not need explained etiologic objectives

Answer 22

Cross-sectional Studies

Question 23

Sampling and analytic methods provide for statistically valid inference to populations

Answer 23

advantages of cross sectional studies

Question 24

Exposure and disease are assessed at the individual level

Answer 24

advantages of cross sectional studies

Question 25

Temporality cannot be assessed

Answer 25

Cross-sectional Studies

Question 26

Randomized clinical trial and Community intervention trials

Answer 26

Experimental studies

Question 27

typical type of study used in clinical medicine

Answer 27

Randomized Clinical Trial (RCT)

Question 28

Are sub-types of cohort studies in which exposure (i.e., treatment) is randomly assigned by the investigator

Answer 28

Randomized Clinical Trial (RCT)

Question 29

The process by which each participant’s treatment is determined by some random mechanism

Answer 29

randomization of RCT's

Question 30

minimizes confounding (known and unknown) results

Answer 30

randomized RCT's

Question 31

create groups (experimental and control) that are not determined by any other factor other than by chance

Answer 31

using randomized RTC's

Question 32

the investigator and/or the participant do not know what arm the participant is in

Answer 32

blinding in RCT's

Question 33

the participant does not know but investigator does know treatment assignment

Answer 33

single blinded

Question 34

where neither participant nor investigator know treatment assignment

Answer 34

double blinded

Question 35

purpose of blinding

Answer 35

to remove bias or systematic error

Question 36

drawing different conclusions depending on their knowledge of which study arm particular participant is in

Answer 36

Information bias

Question 37

study recruiters can be eager to recruit “sick persons” into experimental arm

Answer 37

Selection bias

Question 38

Considerations in experimental studies

Answer 38

Stopping rules Sample size Analysis and Interpretation

Question 39

systematic complete summary of the literature

Answer 39

Systematic Review

Question 40

combined analysis of data from different studies following strict guidelines

Answer 40

Meta-analysis