Lecture 4

Question 1

they observe the outcomes without intervening to affect them

Answer 1

observational studies

Question 2

the reseacher manipilates the exposure (usually drug) to compare it to the standard of care

Answer 2

experimental studies

Question 3

what kind of studies are ;
Cohort studies
case control studies
cross-sectional studies

Answer 3

observational studies

Question 4

subjects are selected based on their exposure status

Answer 4

cohort study

Question 5

__studies follow participants in time:

Answer 5

cohort

Question 6

compares disease prevalence in the exposed and unexposed

Answer 6

prospective cohort

Question 7

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

Answer 7

retrospective cohort

Question 8

maintains temporal sequence (assesses exposure before outcome)

good for assessing rare exposures and rapidly fatal diseases

can study multiple diseases/outcomes from a given exposure

Answer 8

advantages of cohort study

Question 9

can calculate incidence among exposed and unexposed

Answer 9

cohort advantage

Question 10

provides complete description of experience after exposure, including rate of progression and natural history of disease

Answer 10

cohort advantage

Question 11

expensive
inefficient for rare diseases
long followup

Answer 11

disadvantage of cohort

Question 12

cohort study selection of exposed - source depends on

Answer 12

research question

ability to collect exposure or diseased info

Question 13

subjects are selected based on their diseased status

Answer 13

case-control study

Question 14

theoretically should mimic cohort studies , diseased people are compared to non-diseased people

Answer 14

case-control study

Question 15

in a case-control study, cases and controls should be different only on

Answer 15

their past exposure

Question 16

can demonstrate risk indicators and not risk factors due to the retrospective nature of the study design (temporality cannot be assessed)

Answer 16

case-control study

Question 17

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 17

case-control study

Question 18

cases and controls must have an equal

Answer 18

chance of being exposed

Question 19

efficient for rare diseases
relatively efficient in terms of time and money
can study diseases with long latency period
allow for the evaluation of multiple exposures that may increase risk for a specific disease

Answer 19

advantages of case-control studies

Question 20

not optimal for rare exposures, cannot directly compute incidence of disease in exposed and non-exposed persons
temporal relationship cannot be established with certainty
prone to errors in selection of cases/controls and in errors pertaining to the collection of information

Answer 20

disadvantages case-control studies

Question 21

case-control study: selection of \_\_; 
case (disease definition
diagnostic criteria
hospital based or population based
incident or prevalent cases

Answer 21

selection of cases

Question 22

case-control: selection of __;
would be cases if had the disease (similar to cases)
potential for bias and confounding

Answer 22

selection of controls

Question 23

selection of subjects based on neither exposure or disease status

Answer 23

cross-sectional studies

Question 24

most basic study design
“point-in-time” or snapshots information
subject selected without regards to exposure or disease status
does not need explained etiologic objectives

Answer 24

cross-sectional studies

Question 25

sampling and analytic methods provide for statistically valid inference to populations
exposure and disease are assessed at the individual level

Answer 25

advantages of cross-sectional studies

Question 26

temporality cannot be assessed

Answer 26

disadvantage of cross-sectional studies

Question 27

randomized clinical trial

community intervention trials

Answer 27

experimental studies

Question 28

principles of all experimental studies follow those from clinical trials
have a long history in clinical medicine
are sub-types of cohort studies in which exposure is randomly assigned by the investigator

Answer 28

randomized clinical trial

Question 29

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

Answer 29

randomization feature of RCT

Question 30

the primary purpose of ___ is the minimizing of confounding

Answer 30

randomization

Question 31

why randomize in RCT

Answer 31

to create groups that are not determined by any other factor than by chance

Question 32

feature of RCT; the investigator and/or the participant do not know what arm the participant is in

Answer 32

blinding

Question 33

the participant does not know but investigator does know treatment assignment

Answer 33

single blinded

Question 34

neither the participant nor investigator know treatment assignment

Answer 34

double blindee

Question 35

what is the 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

key elements of\_\_\_;
selection of study population
allocation of treatment/intervention
study conduct and compliance 
follow-up and establishing outcomes

Answer 38

RCT

Question 39

considerations in experimental studies (3)

Answer 39

stopping rules, sample size, analysis and interpretation

Question 40

systematic complete summary of the literature

Answer 40

systematic review

Question 41

combined analysis of data from different studies following strict guidelines

Answer 41

meta-analysis