Block Randomized Experiment
A Block Randomized Experiment is a randomized experiment where experiment subjects are first assigned to blocks by way of stratified sampling.
- AKA: Stratified Randomized Experiment.
- Context:
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- Example(s):
- See: Purely Randomized Experiment.
References
2013
- http://en.wikipedia.org/wiki/Randomized_block_design
- In the statistical theory of the design of experiments, blocking is the arranging of experimental units in groups (blocks) that are similar to one another. Typically, a blocking factor is a source of variability that is not of primary interest to the experimenter. An example of a blocking factor might be the sex of a patient; by blocking on sex, this source of variability is controlled for, thus leading to greater accuracy.
- http://en.wikipedia.org/wiki/Blocking_%28statistics%29
- In the statistical theory of the design of experiments, 'blocking is the arranging of experimental units in groups (blocks) that are similar to one another. For example, an experiment is designed to test a new drug on patients. There are two levels of the treatment, drug, and placebo, administered to male and female patients in a double blind trial. The sex of the patient is a blocking factor accounting for treatment variability between males and females. This reduces sources of variability and thus leads to greater precision.
Reducing known variability is exactly what blocking does. Its principle lies in the fact that a variability that can not be overcome (e.g. needing two batches of raw material to produce 1 container of a chemical) is confound or aliased with a(n) (higher/highest order) interaction to eliminate its influence on the end product. High order interactions are usually of the least importance (think of the fact that temperature of a reactor or the batch of raw materials is more important than the combination of the two - this is especially true when more (3, 4, ...) factors are present) thus it is preferable to confound this variability with the higher interaction.
- In the statistical theory of the design of experiments, 'blocking is the arranging of experimental units in groups (blocks) that are similar to one another. For example, an experiment is designed to test a new drug on patients. There are two levels of the treatment, drug, and placebo, administered to male and female patients in a double blind trial. The sex of the patient is a blocking factor accounting for treatment variability between males and females. This reduces sources of variability and thus leads to greater precision.