Exam 2

Question 1

Equation for Prevalence

Answer 1

of individuals with disease/# of individuals considered

Question 2

Equation for incidence density (rate)

Answer 2

of new individuals with disease or disease onset/sum of person-time at risk

Question 3

Equation for cumulative incidence (proportion)

Answer 3

of disease onsets/# at risk at beginning of follow-up

Question 4

What ratio does this apply to?

The odds of exposure (1 row) to (1 column) is 2.0 times the odds among those without ( 2 column)

Answer 4

Odds Ratio

Question 5

What ratio does this apply to?

The risk of (what’s being studied) among those with (primary exposure or 1 row) is 2.0 times the risk among those with (2 row)

Answer 5

Risk Ratio

Question 6

What are quasi-experimental studies?

Answer 6

Community trials that are focused on groups

Question 7

Are randomized clinical trials primarily focused on groups or individuals?

Answer 7

individuals

Question 8

What’s the equation measure for randomized clinical trials? And what is needed to calculate?

Answer 8

Relative Risk is the measure and incidence measure calculations are needed first

Question 9

Whats the equation for relative risk

Answer 9

A/A+B/C/C+B

Question 10

Are cohort observational study participants disease free at baseline? why?

Answer 10

yes, because the study is to see if exposure causes the disease

Question 11

What is the equation used in cohort studies?

Answer 11

Relative Risk

Question 12

What kind of a study is a population-based study followed through time?

Answer 12

Cohort

Question 13

how many time points are there in cohort studies?

Answer 13

at least 2

Question 14

Are cohort studies exposure or outcome based or both?

Answer 14

cohort studies are exposure based

Question 15

Are cross-sectional studies exposure or outcome based or both?

Answer 15

cross-sectional studies are both

Question 16

Are case-control studies exposure or outcome based or both?

Answer 16

case-control studies are outcome based (disease)

Question 17

What is the equation for cross-sectional studies?

Answer 17

Odds Ratio

Question 18

What is the equation for case-control studies?

Answer 18

Odds Ratio

Question 19

What do case-control studies measure?

Answer 19

they measure beyond exposure

Question 20

What study design has potential for recall bias?

Answer 20

case-control studies

Question 21

What is a retrospective study?

Answer 21

A retrospective looks at historical data but at that past point in time of the study the group was disease free

Question 22

What is a prospective study?

Answer 22

A prospective study watches for outcomes, such as the development of a disease, during the study period and relates this to other factors such as suspected risk or protection factor(s). The study usually involves taking a cohort of subjects and watching them over a long period.

Question 23

What is recall bias?

Answer 23

this means that there is always a measurement error when recalling something in the past and bias comes in when there is exposure to the disease that could come out as feeling towards a diagnosis (could be different in disease group vs. the control group)

Question 24

Is cross-sectional studies representative of incidence or prevalence?

Answer 24

prevalence

Question 25

Does risk ratio represent incidence or prevalence?

Answer 25

incidence

Question 26

Does odds ratio represent incidence or prevalence?

Answer 26

prevalence

Question 27

What does Bradford Hill’s criteria do with study designs?

Answer 27

fits into interpreting the strength of the evidence for causal relationships

Question 28

What is temporality?

Answer 28

It is solid evidence that exposure happened before the disease

where exposure preceded development of disease by a period consistent with proposed biologic mechanism

when a sufficient induction / latent period exists

Question 29

What does strength of association mean?

Answer 29

the stronger the association the more likely the exposure-disease relationship is causal

a strong association is less likely than a weak association to be due to confounding bias

RR or OR quantifies the association between exposure and outcome - generally there is a large relative risk or large odds ratio here

Question 30

What is biological gradient/dose response?

Answer 30

the higher the exposure (perhaps to a dose) the higher the risk

strength of association increases with intensity or duration of exposure, as predicted

Question 31

What is plausability?

Answer 31

when there are known or postulated biological mechanisms that help explain exposure-disease relationship - when there is evidence to support and association

examples: contaminated water / cholera, cigarette smoke / lung cancer, promiscuity / AIDS

Question 32

What is consistency?

Answer 32

when other studies using different populations and methodology show similar results

Question 33

What is coherence?

Answer 33

when an association must not seriously conflict with what is already known about natural history or biology of disease

Question 34

What is specificity?

Answer 34

when a specific exposure is associated with only one disease - this may not be applicable to chronic diseases since a specific exposure may be associated with several diseases

Question 35

What is internal validity?

Answer 35

Internal validity refers to how well an experiment is done, especially whether it avoids confounding (more than one possible independent variable [cause] acting at the same time). The less chance for confounding in a study, the higher its internal validity is