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Experimental Design

Experimental Design. Statistical studies are used to obtain reliable information. Planning a Statistical Study. Identify individuals or object of interest Specify variables and protocols for observations Decide whether to use a census or a sample and determine viable sampling method

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Experimental Design

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  1. Experimental Design Statistical studies are used to obtain reliable information.

  2. Planning a Statistical Study • Identify individuals or object of interest • Specify variables and protocols for observations • Decide whether to use a census or a sample and determine viable sampling method • Collect data • Make decisions • List concerns and recommendations

  3. Census Measurements or observations from entire populations are used.

  4. Sample Measurements or observations from a representative part of the population are used.

  5. Simulation A numerical facsimile of real-world phenomena

  6. Experiments and Observation • Observational Study: no change is made in the responses or variable being studied • Experiment: a treatment is imposed in order to observe a possible change in the response or variable being measured

  7. Randomized two-treatment experiment • Subjects are randomly assigned to one of two groups • One group receives treatment under study • Control group receives placebo • Results are compared • Randomization prevents bias • Replication on many subjects assures changes not caused by random chance

  8. Surveys Data is gathered by asking people questions.

  9. Problems with data collection • Some individuals do not respond. • People with strong opinions may be over-represented in voluntary response samples. • There may be a hidden bias in the data collection process. • There may be hidden effects of other variables. • There is no guarantee that results can be generalized.

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