Studied by 2 people
Convenience sample
individuals in the sample are obtained by ‘proximity’ to the researcher
Voluntary sample
individuals have the choice to be included in the sample
Simple random sample (SRS)
each member of the population has an equal chance of being chosen for the sample
Stratified random sample
the population is separated into groups (strata) and an SRS is collected for each of the strata
Cluster sample
the population is separated into groups (clusters) and a RNG is used to select clusters where every individual in that cluster is sampled
Systematic random sample
A RNG is used to select a random individual (starting point) in the population and every nth individual is selected afterwards
Undercoverage
some people are less likely to be chosen
Nonresponse
people can’t be reached or refuse to answer
Response bias
problems in the data gathering instrument/process
Confounding variable
“extra” variable that affects both the response and explanatory variable
Observational study
no treatment imposed; can NOT prove causation
Experiment
treatment imposed; can prove causation
Experimental units
who/what the treatment is given to
Treatment
what is done/not done to the experimental units
Control group
doesn’t get treatment; used as a baseline
Single-blind experiment
either experimenter or experimental units don’t know who gets the treatments
Randomized block design
separate subjects into blocks and then randomly assign treatments within each block
Matched pairs design
subjects are placed in blocks of size two and then randomly assigned treatment
Note 
Flashcard (63)