Exam 2 Flashcards
Equation for Prevalence
of individuals with disease/# of individuals considered
Equation for incidence density (rate)
of new individuals with disease or disease onset/sum of person-time at risk
Equation for cumulative incidence (proportion)
of disease onsets/# at risk at beginning of follow-up
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)
Odds Ratio
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)
Risk Ratio
What are quasi-experimental studies?
Community trials that are focused on groups
Are randomized clinical trials primarily focused on groups or individuals?
individuals
What’s the equation measure for randomized clinical trials? And what is needed to calculate?
Relative Risk is the measure and incidence measure calculations are needed first
Whats the equation for relative risk
A/A+B/C/C+B
Are cohort observational study participants disease free at baseline? why?
yes, because the study is to see if exposure causes the disease
What is the equation used in cohort studies?
Relative Risk
What kind of a study is a population-based study followed through time?
Cohort
how many time points are there in cohort studies?
at least 2
Are cohort studies exposure or outcome based or both?
cohort studies are exposure based
Are cross-sectional studies exposure or outcome based or both?
cross-sectional studies are both
Are case-control studies exposure or outcome based or both?
case-control studies are outcome based (disease)
What is the equation for cross-sectional studies?
Odds Ratio
What is the equation for case-control studies?
Odds Ratio
What do case-control studies measure?
they measure beyond exposure
What study design has potential for recall bias?
case-control studies
What is a retrospective study?
A retrospective looks at historical data but at that past point in time of the study the group was disease free
What is a prospective study?
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.
What is recall bias?
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)
Is cross-sectional studies representative of incidence or prevalence?
prevalence
Does risk ratio represent incidence or prevalence?
incidence
Does odds ratio represent incidence or prevalence?
prevalence
What does Bradford Hill’s criteria do with study designs?
fits into interpreting the strength of the evidence for causal relationships
What is temporality?
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
What does strength of association mean?
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
What is biological gradient/dose response?
the higher the exposure (perhaps to a dose) the higher the risk
strength of association increases with intensity or duration of exposure, as predicted
What is plausability?
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
What is consistency?
when other studies using different populations and methodology show similar results
What is coherence?
when an association must not seriously conflict with what is already known about natural history or biology of disease
What is specificity?
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
What is internal validity?
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
