Cluster Sampling

# Cluster Sampling - Cluster Samples Review Question You have data on 60 students which consists of 20 students for each of three classrooms 1 For

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Cluster Samples Review Question You have data on 60 students, which consists of 20 stu- dents for each of three classrooms. 1. For the 60 60 error covariance matrix, which ele- ments are zero?

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Cross-section data traditional: random sample (observations indepen- dent) recent: cluster sample (observations dependent) Cluster - a group from which multiple observations are drawn classroom - multiple students sampled &rm - multiple workers sampled
Source of Dependence common (often unobserved) characteristics students in a classroom common teacher common class environment parent e/orts to secure teacher common education level (&rm requirement)

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Example: Student Test Score Performance y ig test score, student i in classroom g x g class size in classroom g y ig = & 0 + 1 x g + u ig cor u ig ; u jg ± > 0 u ig = v g + " ig v g common unobserved component (teacher, class envi- ronment) " ig cov u ig ; u jg ± = ± 2 v cor u ig ; u jg ± = ± 2 v ± 2 v + ± 2 " ² ± 0
Standard Error Adjustment n constant group size x g does not vary within groups V c ^ 1 j X ± conventional OLS variance formula V ^ 1 j X ± correct variance formula Moulton (1986): V ^ 1 j X ± V c ^ 1 j X ± = 1 + ( n 1) ± n = 1 : conventional OLS standard errors correct ± = 0 : conventional OLS standard errors correct

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## This note was uploaded on 12/26/2011 for the course ECON 245a taught by Professor Staff during the Fall '08 term at UCSB.

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Cluster Sampling - Cluster Samples Review Question You have data on 60 students which consists of 20 students for each of three classrooms 1 For

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