solutions of samplemidterm2

# solutions of samplemidterm2 - 1. a) explanatory var....

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a) explanatory var. – treatment type response var. – survival time after surgery b) Individuals are observed without any imposition of some treatment. c) No. An observational study is a poor way to gauge the effect of an intervention. On the other hand, experiments can give good evidence for causation. 2. μ x = np = 24 σ 2 x = npq = 9.6 a) μ z = 1/2μ x + 3μ y + 4 = 12+24+4 = 40 b) σ 2 z = 1/4 σ 2 x + 9 σ 2 y = 2.4 + 9 = 11.4 σ z = 3.37639 3. a) Placebo : a dummy treatment. Group 2 receives placebo which enables us to control the effects of lurking variables. Control : the first basic principle of statistical design of experiments. Most simply by comparing two or more treatments (in this context the Group 2 is a control group), control the effects of lurking variables on the response. Double-blind : neither the subjects nor the people who have contact with them know which treatment a subject received. Random

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## This note was uploaded on 03/30/2008 for the course STAT 155 taught by Professor Unknown during the Summer '07 term at UNC.

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solutions of samplemidterm2 - 1. a) explanatory var....

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