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Chapter 13 - from different treatments For example blinding...

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Chapter 13 Experiments ActivStats: 13 Read: Chapter 13 OBSERVATIONAL STUDY - a study based on observed data with no manipulation of factors employed (for example a survey ). Usually used to estimate population parameters Retrospective – data consist of past outcomes Prospective – data will consist of future outcomes EXPERIMENTS - a study based on manipulation of factors (treatments) employed and analysis of observed responses . Usually used to determine causal relationship. A researcher must identify at least one explanatory variable, called factor, and its values ( levels) to be assigned. Any combination of different factors and their levels is called a treatment. A researcher observes responses to different treatment. Principles of Experimental Design. 1. Control. C ontrol sources of variation other than coming
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Unformatted text preview: from different treatments. For example blinding either subjects or those who evaluate responses or both • single-blinding • double-blinding Placebo- fake treatment 2. Block. Block or match subjects to reduce variability of responses to the same treatment. 3. Randomize. An experiment requires a random assignment of experimental units to treatments. Randomization allows to equalize the effects of uncontrollable sources of variation. • completely randomized design- all experimental units have the same chance to receive any treatment • randomized block design- randomization occurs only within blocks 4. Replicate. Replicate over as many subjects as possible and replicate entire experiment with different groups of subjects...
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Chapter 13 - from different treatments For example blinding...

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