Voluntary Response Sample
a large group of individuals is invited to respond and all people are counted, usually biased
Confounding variable
when the levels of one factor are associated with the levels of another factor in such a way that their effects can't separated
Population
The entire group of individuals whom we hope to learn
Sample
a representative subset of a population
Convenience Sample
consists of all of the individuals who are conveniently available. often fail to be representative
Biased Sample
when members of a population are systematically more likely to be selected in a sample than others
simple random sample
a sample where each set of n elements in the population has an equal chance of selection
stratified sampling method
Dividing a population into smaller groups based on shared characteristics
cluster sampling method
whole population is divided into groups, groups randomly selected, then census is taken from each group
undercoverage bias
when some members of a population aren't properly represented
response bias
tendency of respondent to answer untruthfully or misleadingly
nonresponse bias
tendency of a respondent to be unwilling or unable to respond
systematic sample
a sample technique where the researcher chooses members from a population by selecting a random starting place and picking based on a fixed sampling interval
experimental units
smallest physical entity which a treatment can be applied
subjects
members of the control or treatment group in an experiment
treatment
the item being studied in an experiment
factor
the variable being manipulated by the experimenter
level
different values of the factor
placebo effect
a neutral treatment that isn't supposed to have an effect on the dependent variable of the experiment, but may because the idea of treatment
control group
subjects who didn't receive treatment
randomization
practice of using a chance method to assign subjects to treatments
completely randomized experiment
an experiment design where the treatments are designed completely at random
statistically significant
determination by an analysis that the results of an experiment aren't explainable by chance alone
replication
practice of assigning each treatment to many experimental subjects
double-blind experiment
an experiment that neither the subjects nor the evaluators know who's the treatment group nor who's the control group
block design
the arranging of an experimental unit into groups that are similar to one another
match pair design
a special case of a randomized block design that can be used when the experiment has only two treatment conditions and subjects can be grouped into pairs based on a blocking variable