design study
one that employs a systematic arrangement or pattern for collecting data
observational unit
entities on which measurements or observations can be made.
sampling units
observational units are often selected from a larger population of such units
target population
A collection of sampling units about which we want to draw conclusions.
sampling frame
A list of all sampling units in the target population.
sample
A subset of the target population from which observations are actually obtained, and from which conclusions about the target population will be drawn
undercoverage
The sampling frame may not include some elements of the target population
overcoverage
The sampling frame may include some elements that are not members of the target population
sampling design
a pattern, arrangement or method used for selecting a sample of sampling units from the target population
sampling plan
the operational plan, including the sampling design, for actually obtaining or accessing the sampling units for the study
sampling error
Error inherent in the sampling process
non-sampling error
These are really errors
selection bias
a systematic tendency on the part of the sampling method to underrepresent or exclude one or more kinds of the sampling units from the sample
bias
a distortion of the results of a statistical procedure
probability sampling
a method of choosing a sample using a pre-specified chance mechanism
simple random sampling
Each potential sample has the same chance of being chosen
stratified random sampling
Sampling units are divided into distinct strata, and a simple random sample are taken from each stratum
cluster sampling
Units in close proximity are grouped in clusters, and clusters are sampled
multistage sampling
many samples are taken in stages
experimental unit
a sampling unit selected for use in a controlled experiment
response
a measurement or observation of interest that is made on an experimental unit
effect
The change in the average response between two factor levels or between two combinations of factor levels.
factor
A quantity that is thought to influence the response
experimental factor
A factor that is purposely varied by the experimenter
nuisance factor
A factor that cannot be controlled by the experimenter
level
a value assumed by a factor in an experiment.
treatments
The combinations of levels of experimental factors for which the response will be observed.
experiment
a study in which some treatments are deliberately imposed on the experimental units in order to observe the effect
completely randomized design
Treatments assigned to experimental units completely at random
randomized complete block design
Experimental units grouped into blocks and all treatments are assigned at random within each block
causality
to show that changing the treatment will cause a change in the response
randomized controlled experiments
Controlled experiments in which treatments are assigned at random to experimental units
observational study
a designed study which observes individuals and measures variables of interest but does not attempt to influence the responses
cohort studies (aka prospective)
treatment" and "control" groups are established based on the hypothesized cause
case-referent studies (aka retrospective)
groups are formed based on the response (i.e., effect)
sampling surveys
use a sample of sampling units obtained from a population to obtain information about the whole population
frequency histogram
shows static pattern of variation of a data
time series plot (line plot)
shows pattern of variation evolving over time
data
Facts that convey information from which conclusions can be drawn
statistics
a science that deals with the collection, organization, analysis, interpretation, and presentation of data to come up with meaningful information