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51 Cards in this Set

  • Front
  • Back
an informal study in which the experience of a group of patients or only one patient is described
case report or case series
studies which use groups of individuals as the unite of analysis
ecological studes

Advantages: quick, helop with hypothesis
Disadvantages: poorly suited for causal inference. thos exposed may not be those with the disease
two or mjore assessments are made simultaneously on the subjects in this type of study
this study may use descriptive statistics such as age-specific disease rates that summarize the disease burden
ecological studies
groups selected on whether they have experienced the outcome
case-control study
an odds ratio greater than one indicates
exposure is associated with increase risk of disease
odds ratio of 1
means no association between exposure and risk of disease
odds ratio less than 1
means exposure is associated with a decrease risk of disease
study where it is imposible to compute disease risks in exposed group and unexposed goup - oods ratio is used instead
case-control study

subjects are selected according to whether or not they have experienced the outcome or not. you cant compute the disease risks because the numbers of cases and controls have been fixed by the study design and not by nature.
a case control study which includes all cases occurring in a defined group during a certain time period
population based
in clinic based case-contro studies why might the data be distorted
patients may be reffered from a differnt population - so the computed relative risks may be distorted.
When case and control groups are inappropriately matched
selection bias
formal follow up of individuals over time
cohort (follow up) study
a cohort study where all outcomes in the final analysis would have occured before the study even started
retrospective cohort study
a cohort study where cohort would be directly observed over time
prospective cohort study
the ascertainment of the endpoints is particularly inportant in what study
cohort studies
what are the study measurements in a cohort vs. case-control study
cohort : disease outcome
Case-control: exposure history
can you measure the risks in a cohort or a case-control study
you can measure risks in a cohort but not a case control study
what are the three ways you can measure relative risk in a cohort study
risk ratio, rate ratio, odds ratio
how do you measure relative risk in a case control study
odds ratio.
a cohort study in which athe investigator determines the exposure
clinical trial
helps ensure that the interventions under study are being tested on similar patients

in small samples may still be imbalanced but in large samples imbalance is unusual
when investigators are kept ignorant of which patients are on which treatments.
if the investigators or patients (but not both) in a study are kept ignorant of treatment assignments, the study is called
single blind
if if both investigator and pt is unaware of of assignments the study is called
double blind
historical controls
the control group is a group of people who in the past have been treated a particular way -- they are compared with the group getting the new treatment.
poor evaluation method - groups of patients will obviously differ quite a bit
in what study might patient outcome affect measurement of the exposure in individual subjects
in what tho type of studies involve follow-up of subjects over time
cohort and randomized clinical
in what two studies can the risk or rate of an outcome for an individual be calculated according to exposure status
cohort and randomized clinical
what type of study controlls for confouding affects
the final analysis which includes a comparison based on randomization assignments regardless of what treatment the patient actually received
intent-to-treat analysis

includes thos who have crossed over between study treatments
an analysis of a randomized experiment based on subjects who actually receive and comply with assigned treatments
efficacy analysis - not based on the entire randomly-created groups, because of patients who drop-out or cross-over between study treatments
when the results of a study can be applied to a general population, we say that the study results are
generalizable or externally valid
refers to the correctness of the study conclusions regarding the particular study population
internal validity
a descriptive study
involves no comparisons
if there are comparisons but the investigator only watched what would have happened anyway the study is called a
analytic observational study
if there are comparisons and the investigator determined the treatment of the subjects, then the study is a
clinical trial (intervention study)
if diseased and non-diseased groups are separately chosen for the study then what kind of observational study is it
if subjects with known exposure are followed up over time then what kind of observational study is it
if the unit of analysis is groups of people, and individuals are not questioned or measured, then what kind of observational study is it
if one group is investigated and disease and exposure status are determined at the same time what kind of observational study is it
what is the concern with a descriptive study
precision and bias
what is the concern with a case-control study
selection bias (do cases and controls correspond?

information bias (did the presence/absence of disease affect the data obtained)
what is a concern with a cohort study
follow up time (where exposed and unexposed groups followed and endpoints determined with equal intensity and w/o bias)
what is the concern with clinical trial
what kind of controls? bias?
a dose-response relationship
if a gradient of risk can be demonstrated such that greater exposure causes higher disease risk, then causality is implied
a repeated finding suggests the possibility of causality, particularly if the result is foundin studies of different designs performed in different population group
consistent association
a series of analyses that show an exposure to be associated with virually every disease is suspect
specific association
the ability of a study to apply to populations other than the one actually studied
external validity - also called generalizability
response bias is also known as
informaiton bias
odds ratio is used to evaluate risk in what kind of study
case control