Design Strategies and Statistical methods in Analytic Epidemiology

Question 1

Analytic studies

Answer 1

evaluate hypotheses about associations between exposure and outcome variables; attempt to answer why and how a health-related state or event occurred; have a comparison group

Question 2

Observational exploratory study

Answer 2

researchers examine relationships between variables; useful for identifying cause-effect relationships

Question 3

Observational analytic study

Answer 3

begins with a hypothesis and evaluates associations between exposure and outcome variables

Question 4

Types of analytic observational studies

Answer 4

case-control studies
cohort
case-crossover
nested case-control

Question 5

Incidence

Answer 5

new cases

Question 6

Prevalence

Answer 6

existing cases

Question 7

Case-control study

Answer 7

investigates the presence of a potential risk factor between cases and controls

Question 8

Exposure status

Answer 8

collected in a similar manner between cases/controls to avoid bias

Question 9

Measuring the association between exposure and outcome variables is

Answer 9

the appropriate measure of association to use as it depends on the nature of the data

Question 10

Bias

Answer 10

systematic error in the collection or interpretation of epidemiologic data

Question 11

Results in inaccurate over or under estimation of the association between exposure and outcome

Answer 11

bias

Question 12

Types of bias in case-control studies

Answer 12

selection, observational, misclassification, confounding

Question 13

Confounding

Answer 13

an outside factor is associated with a disease outcome and is independently linked with an exposure (age, sex, education level, smoking)

Question 14

Controlling for bias

Answer 14

matching

Question 15

Matching

Answer 15

a strategy in which the distribution of potential confouding factors is forced to be similar between the cases and controls

Question 16

2 types of selection bias in cohort studies

Answer 16

healthy worker effect, loss to follow-up

Question 17

2 types of observation bias in case-control studies

Answer 17

recall, interviewer

Question 18

Recall bias

Answer 18

differential accuracy of recall about past exposure between cases (with disease) and controls (without disease)

Question 19

Interviewer bias

Answer 19

differential accuracy of exposure information due to the interviewer probing questions differently between cases and controls

Question 20

Misclassification

Answer 20

error in classifying exposure or outcome status

Question 21

Several variables considered as potential confounders

Answer 21

age, sex, educational level, smoking

Question 22

Confounder

Answer 22

X

Question 23

Strengths of Case-Control Studies

Answer 23

effective for rare outcomes; requires less time, money due to small size; yields the odds ratio (good estimate of relative risk)

Question 24

Bias

Answer 24

deviation of the results from the truth

Question 25

Weaknesses of Case-Control Studies

Answer 25

limited to one outcome condition; does not provide incidence, relative risk, or natural history; less effective than a cohort study at establishing time sequence of events; potential recall and interviewer bias; potential survivor bias; does not yeild incidence and prevalence

Question 26

Ratio for Case-Control studies

Answer 26

Odds Ratio (paired data)

Question 27

Ratio for Cohort (attack rates)

Answer 27

Risk Ratio

Question 28

Ratio for Case Crossover

Answer 28

Odds Ratio (unpaired data)

Question 29

Ratio for Cohort (peron-time rates)

Answer 29

Rate Ratio

Question 30

Prospective Cohort Study

Answer 30

goes forward in time; measures exposure status and association to an outcome

Question 31

Retrospective Cohort Study

Answer 31

goes back in time; identifies a cohort with already available exposure and outcome data

Question 32

Effect Modification

Answer 32

association between an exposure and disease outcome is changed by the level of an extrinsic factor

Question 33

Selection bias

Answer 33

the selection of cases and controls based in some way on the exposure

Question 34

Healthy worker effect

Answer 34

occurs in cohort studies when workers represent the exposed group, and a sample from the general population represents the unexposed group

Question 35

Loss to follow up

Answer 35

occurs in cohort studies when researchers lose contact with study participants, resulting in unavailable outcome data on those people

Question 36

Cases

Answer 36

with health-related state/event

Question 37

Control

Answer 37

without health-realted state/event

Question 38

Odds ratio

Answer 38

measures strength or association between exposure and disease variables

Question 39

2x2 contigency table

Answer 39

commonly used to summarize the relationship between exposure and health outcome variables

Question 40

What does the Odds ratio (OR) compare?

Answer 40

the odds of the disease among exposed individuals to the odds of disease among unexposed individuals

Question 41

Observer bias

Answer 41

Misclassification of data because of differences in observer interpretation or expectations regarding the study