protocol
the written plan of the study
research question
the objective of the study, the uncertainty the investigator wants to resolve.
background, significance
these two sections of a protocol set the proposed study in context and give it rationale
observational study
study in which the researcher takes a passive role studying subjects
clinical trial
the researcher applies an intervention and examines its effects on these events
cohort studies
observations are made in a group of subjects that is followed over time
cross-sectional studies
observations are made on a single occasion
prospective study
cohort study that begins in the present and follows subjects into the future
retrospective study
cohort study that examines information and specimens that have been collected in the past
Case-control study
study in which the investigator compares a group of people who have a disease or condition with another group who does not.
descriptive
studies that "explore the lay of the land
analytic
studies that evaluate associations to permit inferences about cause-and-effect relationships
randomized blinded trial
two groups created by a random process, and a blinded intervention
inclusion and exclusion criteria
specifications that define the target population: the kinds of patients best suited to the research question.
predictor variable
in considering the association between two variables, the one that occurs first or more likely on biologic grounds to be causal
outcome variable
in considering the association between two variables, the one that occurs last or more likely on biologic grounds to be the effect of another variable
intervention
a special kind of predictor variable that the investigator manipulates
confounding variables
other predictors of the outcome, that could be related to the intervention or predictor variable, and confuse the interpretation of the findings.
hypothesis
specific version of the research question that establishes the basis for tests of statistical significance.
sample size
the number of subjects needed to observe the expected difference in outcome between study groups with reasonable probability
internal validity
the degree to which the investigator draws the correct conclusions about what actually happened in the study
external validity
the degree to which conclusions of a study can be appropriately applied to people and events outside the study
generalizability
another word for external validity.
inferences
drawn from findings in a study to the nature of the universe around it.
random error
a wrong result due to chance- sources of variation that are equally likely to distort estimates from the study in either direction.
systematic error
a wrong result due to bias- sources of variation that distort the study findings in one direction.
sampling error
errors that threaten inferences from the study subjects to the population
measurement error
errors that threaten the inferences from the study measurements to the phenomena of interest.