Fixed, Random and Mixed Models

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Fixed, Random and Mixed Models
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Definitions

• Fixed Effects factors for which the only levels
  under consideration are this in the experiment
• Random Effects Factors for which the levels are
  a random sample of the total number of levels in
  the population for that factor.

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Definitions

• Fixed Model All factors are fixed
• Random Model All factors are random
• Mixed Model Both fixed and random factors are in
  the model

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Examples

• Fixed Model
• Random Model Kutner p959
• Mixed Model O L p977

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Random Model
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Estimation

• What are the unknown parameters?
• What do we want to test?
• Hypotheses Testing

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Example KutnerCh24 Table 01
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Nested DesignKutner Ch 28 Table 1
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Instructors
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What is the experimental unit?What is the
sampling unit?Model Fixed, Random Mixed
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What do we want to test?
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Example

• Fixed
• Random
• Mixed

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Two Factor Example OLp977 Table 17.1

• Fixed
• Mixed - Interactions are random if one of the
  factors is random

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Example
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Additional Topics

• Split Plot
• Repeated measures
• RCB Split Plot Repeated measures with covariates