Session #4

Question 1

observe the outcomes without intervening to affect them

Answer 1

obervational studies

Question 2

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

Answer 2

experimental studies

Question 3

what are three examples of obervational studies?

Answer 3

• cohort studies
• case-control studies
• cross sectional studies

Question 4

how are ppl in cohort studies selected?

Answer 4

based on their exposure status

*cohort studies follow participants in time

Question 5

what is a prospective cohort ?

Answer 5

compares disease prevalence in the exposed and unexposed

Question 6

what is a retrospective cohort

Answer 6

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

Question 7

what are the main advantages for cohort studies?

Answer 7

• good for RARE EXPOSURES (not diseases)
• good for calculating INCIDENCE among exposed and unexposed
• -can study multiple diseases
• -minimize error
• -maintains temporal sequence

Question 8

what is the main disadvantage to cohorts?

Answer 8

inefficient for RARE DISEASES (good for exposures)\

-long follow up

Question 9

how are subjects selected for case-controlled studies?

Answer 9

-subjects are selected based on their disease status

Question 10

in case-control studies, cases and controls should be different only in what regard?

Answer 10

past exposure

*theoretically, these should mimic cohort studies

Question 11

what can case control studies demonstrate?

Answer 11

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

Question 12

how are case-control studies set up?

Answer 12

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

*cases and controls must have had an EQUAL CHANCE OF BEING EXPOSED

Question 13

what is the main advantage for case-control studies?

Answer 13

• good for rare DISEASES
• good for long latency periods
• not expensive
• can evaluate multiple exposures

Question 14

what is the main disadvantage for case-control study?

Answer 14

• not good for RARE EXPOSURES

- cannot DIRECTLY compute incidence of disease in exposed and non-exposed persons

Question 15

how are cross-sectional studies set up?

Answer 15

-selection of subjects based on neither exposure or disease status

Question 16

how are cross-sectional studies set up?

Answer 16

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

Question 17

what are the advant of cross sectional

Answer 17

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

Question 18

what is the purpose of randomization in RCTs?

Answer 18

to minimize confounding variables

• to create groups that are not determined by another factor other than by chance
• to minimize confounding (known and unknown)

Question 19

what is the purpose of blinding?

Answer 19

to remove bias or systematic error

Question 20

what is informed bias?

Answer 20

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

Question 21

selection bias

Answer 21

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

Question 22

what is the difference btw systematic reviews and meta analysis?

Answer 22

systematic = complete summary
meta-analysis = combined analysis of data from different studies