Statistics Vocab (Sampling)

biased
any systematic failure of a sampling method to represent its population

block
when groups of experimental units are similar, they are gathered into these groups

census
a sample that consists of the entire population

cluster
sampling design in which entire groups are chosen at random

completely randomized
type of experiment in which all experimental units have an equal chance of receiving any treatment

confounding
when the levels of one factor are associated with the levels of another factor so their effects cannot be separated

control
aspects of the experiment that we know may have an effect on the response, but that are not the factors being studied

experimental units
individuals on which an experiment is done

factor
variable whose levels are controlled by the experimenter

heterogeneous
not similar in makeup

homogeneous
similar in makeup

level
specific values that the experimenter chooses for a factor

matched pairs
type of study in which subjects who are similar in ways not under study may be grouped together and then compared with eachother on the variables of interest

multistage
sampling schemes that combine several sampling methods

nonresponse
type of bias that is problematic because the intended sample is incomplete

observational study
information based on data in which no treatments have been assigned to subjects

outcome
an individual result of a component of a simulation

placebo
treatment known to have no effect, administered so that all groups experience the same conditions

placebo effect
the tendency of many human subjects to show a response even when administered a fake treatment

population
the entire group of individuals or instances about whom we hope to learn

prospective
observational study in which subjects are followed to observe future outcomes

random behavior
an occurrence for which we know what outcomes could happen, but not which particular values will happen

randomization
process by which each individual is given a fair chance of selection

response
type of bias that is problematic because false information may be given

retrospective
observational study in which subjects are selected and their previous conditions or behaviors are determined

sample
a (representative) subset of a population, examined in hope of learning about a population

sample survey
a study that asks questions of a sample drawn from some population in the hope of learning something about the entire population

sampling frame
a list of individuals from which the sample is drawn

sampling variability
the natural tendency of randomly drawn samples to differ, one from another

simple random
sampling design in which each set of n elements in the population has an equal chance of selection

simulation
models random events by using random numbers to specify outcomes with relative frequencies that correspond to the true real-world relative frequencies we are trying to model

single blind
when either the subjects or the people who have contact with them do not know which treatment a subject has received

statistically different
when an observed difference is too large to believe that it is likely to have occurred naturally

strata
a subdivision of the population

stratified
sampling design in which the population is divided into several strata, and random samples are then drawn from each stratum

subjects
people who are studied

systematic
sample drawn by selecting an individual from a list and then each of the next n individual from the sample frame

treatment
the process or intervention applied to randomly assigned experimental units

trial
the sequence of several components representing events that we are pretending will take place

undercoverage
type of bias that is problematic because some groups are not represented in the sample

voluntary response
type of bias that is problematic because those who volunteer tend to have strong negative opinions

voluntary response
sampling design where individuals can choose on their own whether to participate in the sample

wording bias
a type of response bias where the question is posed to achieve a desired result