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Stephen H. Bell
Bell Eval, LLC
Researcher
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SCHOLARLY PAPERS
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Scholarly Papers (1)
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1.
External Validity Bias of Purposive and Random Site Selection When Sites Can Opt Out: Evidence from the Head Start Program
Number of pages: 35
Posted: 08 May 2025
Robert Olsen
, Stephen H. Bell and
Emily Diaz
Rob Olsen LLC, Bell Eval, LLC and Westat
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