Sampling Designs
Uses
- Different sampling designs may be chosen to reduce noise or the effects of nuisance variables in your data.
- Experimental design is the design of any information-gathering
exercise where variation is present, whether under the full control of
the experimenter or not.
In the design of experiments, the experimenter is interested in the
effect of some process or intervention (the "treatment") on some
objects (the "experimental units"). Design of experiments is thus a
discipline that has very broad application across all the natural and
social sciences and engineering.
Designs
- Randomization: Random assignment is the process
of assigning individuals at random to groups or to different groups in
an experiment.
- Replication: Measurements are usually subject to
variation and uncertainty. Measurements are repeated and full
experiments are replicated to help identify the sources of variation,
to better estimate the true effects of treatments, to further
strengthen the experiment's reliability and validit
- Stratified Sampling: To
control the effects of a variable with possible importance but no
direct impact on the question, you can setup a procedure that assures
that the different units in your population are equally likely to be
chosen.
- Blocking: Blocking is the arrangement of
experimental units into groups (blocks) consisting of units that are
similar to one another. Blocking reduces known but irrelevant sources
of variation between units and thus allows greater precision in the
estimation of the source of variation under study.
- Factorial Design: Use of factorial experiments
instead of the one-factor-at-a-time method. These are efficient at
evaluating the effects and possible interactions of several factors
(independent variables).
How this is done
- Randomized Block Design: Effective in removing
nuissance effects, sources of variation that may effect the results
from our study, but not the primary focus of the study - "Block what
you can, randomize what you can not".
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Example
last modified: 4/14/15