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Learn the essential concepts of experimental design - randomization and replication - to ensure fair group comparisons and accurate results. Explore two major designs: Completely Randomized Design and Randomized Block Design, with practical examples included.
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Design of Experiments Jim Bohan Manheim Township School District jim_bohan@mail.mtwp.k12.pa.us
Three Requirements • Comparison • Groups that are a similar as possible. • How do we make groups as similar as possible? • Randomization • Minimize the effect of confounding influences and lurking variables by spreading these effects equally throughout the groups. • Replication • Is the sample size sufficient so that the differences in responses is due to treatments and not chance?
Two Major Designs • Completely Randomized Design • Randomized Block Design
Completely Randomized Design Example: Random Assignment Treatment 1 Results Treatment 2 Results Compare Control Results
Randomized Block Design • Example: Random Assignment Treatment 1 Results Block 1 Compare Treatment 2 Results Compare Treatment 1 Results Block 2 Compare Treatment 2 Results