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Get out homework and discuss with neighbor. Be prepared with any questions you might have.

Get out homework and discuss with neighbor. Be prepared with any questions you might have. Designing Experiments, cont. Section 5.2 . Cautions About Experimentation.

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Get out homework and discuss with neighbor. Be prepared with any questions you might have.

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  1. Get out homework and discuss with neighbor. • Be prepared with any questions you might have.

  2. Designing Experiments, cont. Section 5.2

  3. Cautions About Experimentation • A Randomized Comparative Experiment depends on our ability to treat all the experimental units identically in every way EXCEPT the actual treatments being compared.

  4. Cautions About Experimentation • Attention to detail • How can you ensure that every unit receives exactly the same treatment?

  5. Cautions About Experimentation • Double-blind experiment • Neither the subjects nor the people who have contact with them know which treatment a subject received What are some examples of an experiment that can’t be blind? Double-blind?

  6. Examples • http://articles.latimes.com/2011/may/09/health/la-he-unreal-greys-anatomy-20110509 • http://www.thealzcenter.com/trials/

  7. Cautions About Experimentation • Lack of realism • Setting, treatment, or subjects may not realistically duplicate the conditions we want to study Read Examples 5.14 & 5.15 on p. 300

  8. Cautions About Experimentation • Completely randomized designs are simple but often not as good as more sophisticated designs

  9. Cautions About Experimentation • Matched pairs design • Compares two treatments together in pairs • An example of block design Read example 5.16 p. 301

  10. Cautions About Experimentation • Block design • Block – a group of units (subjects) that are known to be similar in a way that’s expected to affect response to treatment • Random assignment to each treatment is carried out separately within each block

  11. Example • Read Example 5.17, 5.18, & 5.19 p. 302 & 303

  12. Homework • Exercises 5.43, 5.44, 5.45

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