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A Critique of the Statistical Analysis of the OEO Experiment in Performance Contracting OEO

Klein, Stephen P.; O'Connor, Edward F., Jr.
Publication Year:
Report Number:
ETS Research Bulletin
Document Type:
Page Count:
Subject/Key Words:
Experimental Groups, Office of Economic Opportunity, Performance Contracts, Private Schools, Program Evaluation, Public Schools, Remedial Instruction, Statistical Analysis


The experimental students in the OEO experiment were generally lower scoring and less affluent than control students. OEO's statistical analysis used a variety of statistical procedures to adjust for the initial differences in the experimental groups. A reanalysis of the data using a chi-square technique demonstrate that the adjusted posttest differences between the experimental groups were biased against the performance contractors because the differences were not independent of the pretest means. These biases are discussed in terms of differential growth rates, specification error, and errors of measurement. The random assignment of schools to the experimental and control conditions would have avoided many of these problems. (33pp.)

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