The Sensitivity of Experimental Impact Estimates: Evidence from the National JTPA Study
AbstractThe recent experimental evaluation of the U.S. Job Training Partnership Act (JTPA) program found negative effects of training on the earnings of disadvantaged male youth and no effect on the earnings of disadvantaged female youth. These findings provided justification for Congress to cut the budget of JTPA's youth component by over 80 percent. In this paper, we examine the sensitivity of the experimental impact estimates along several dimensions of construction and interpretation. We find that the statistical significance of the male youth estimates is extremely fragile and that the magnitudes of the estimates for both youth groups are sensitive to nearly all the factors we consider. In particular, accounting for experimental control group members who substitute training from other providers leads to a much more positive picture regarding the effectiveness of JTPA classroom training. Our study indicates the value of sensitivity analyses in experimental evaluations and illustrates that experimental impact estimates, like those from nonexperimental analyses, require careful interpretation if they are to provide a reliable guide to policymakers.
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Bibliographic InfoPaper provided by National Bureau of Economic Research, Inc in its series NBER Working Papers with number 6105.
Date of creation: Jul 1997
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Publication status: published as James J. Heckman, Jeffrey Smith. "The Sensitivity of Experimental Impact Estimates (Evidence from the National JTPA Study)," in David G. Blanchflower and Richard B. Freeman, editors, "Youth Employment and Joblessness in Advanced Countries" University of Chicago Press (2000)
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Other versions of this item:
- James J. Heckman & Jeffrey Smith, 2000. "The Sensitivity of Experimental Impact Estimates (Evidence from the National JTPA Study)," NBER Chapters, in: Youth Employment and Joblessness in Advanced Countries, pages 331-356 National Bureau of Economic Research, Inc.
- C93 - Mathematical and Quantitative Methods - - Design of Experiments - - - Field Experiments
- H43 - Public Economics - - Publicly Provided Goods - - - Project Evaluation; Social Discount Rate
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