Lecture 4: Study Design

Question 1

observational studies

Answer 1

outcomes observed w/ out intervention

Question 2

experimental studies

Answer 2

researcher manipulates exposure to compare to standard

Question 3

types of observational studies

Answer 3

1. cohort
2. case-control
3. cross-sectional

Question 4

cohort study

Answer 4

subjects selected based on exposure

Question 5

types of cohort study

Answer 5

prospective & retrospective

Question 6

prospective cohort study

Answer 6

compares disease prevalence in the exposed and unexposed

Question 7

retrospective cohort study

Answer 7

begins w/ exposure of interest & probe back for exposure

Question 8

advantages of cohort studies

Answer 8

good for rare exposures; rapid fatal diseases
calculate incident of exposed & unexposed

assess exposure before outcome, study multiple disease/outcome,, decrease error in ascertainment of exposure, complete description = rate of progression & history

Question 9

disadvantages of cohort studies

Answer 9

inefficient for rare diseases

expensive, long follow up, influenced by secular behavior, diagnostic trends

Question 10

case-control studies

Answer 10

subjects selected based on disease status (diseased VS non-diseased)
mimic cohort
ID risk indicators
assessed retrospectively
case & controls differ ONLY on past exposure

Question 11

advantages of case-control studies

Answer 11

efficient for rare diseases, time & $ efficient, can study diseases with long latency periods, evaluate multiple exposures for increase risk for disease

Question 12

disadvantages of case-control studies

Answer 12

cannot directly compute incidence, cannot establish temporary relationships, not optimal for rare diseases

Question 13

cross-sectional studies

Answer 13

subjects selected based on NEITHER exposure nor disease status
most basic
“snapshot” in time

Question 14

advantages of cross-sectional studies

Answer 14

stats valid inference to population, exposure & disease assessed at individual level

Question 15

disadvantages of cross-sectional studies

Answer 15

temporality cannot be assessed

Question 16

types of experimental studies

Answer 16

randomized clinical trial & community intervention trials

Question 17

randomized clinical trial (RCT) features

Answer 17

randomized - random mechanism for selection = decrease confounding
blinding - investigator and/or participant do NOT know

Question 18

types of blinding

Answer 18

single & double

Question 19

single blinding

Answer 19

only participant does NOT know

Question 20

double blinding

Answer 20

neither participants and investigators do NOT know

Question 21

key elements of RCT

Answer 21

1. selection of study population
2. allocation of treatment
3. study conduct & compliance
4. follow-up & establish outcomes

Question 22

considerations of RCT

Answer 22

stopping rules, sample size, analysis & interpretation

Question 23

systematic review

Answer 23

systematic complete summary of the literature

Question 24

meta-analysis

Answer 24

combined analysis of data from different studies following strict guidelines