experiments Flashcards
experimental units
individuals that are studied; people, plants, things
subjects
when experimental units are people
outcome (response)
what is measured on each experimental unit
treatments
procedures applied to each experimental unit
randomized experiment
investigator assigns the treatment to the experimental units at random
double blind
neither investigators nor the subject know who has been assigned the treatment
completely randomized
no restriction which subjects may be assigned the treatment
randomized block
subjects are divided into blocks in such a way that the subjects in each block are the same or similar with regard to a variable that is related to the outcome
observational study
used when you can not randomly assign treatment
investigators DO NOT assign treatment
COHORT
group of subjects is studied to determine whether various factors of interest are associated with an outcome
prospective
subjects are followed over time
cross-sectional
measurements are taken at one point in time
retrospective
subjects are sampled after the outcome has happened
case-control
two samples are drawn
confounding
difficult to tell whether a difference in outcome is due to the treatment or some other difference between control and treatment
