Suchergebnisse

To assess nonexperimental (NX) evaluation methods in the context of welfare, job training, and employment services programs, the authors reexamined the results of twelve case studies intended to replicate impact estimates from an experimental evaluation by using NX methods. They found that the NX methods sometimes came close to replicating experimentally derived results but often produced estimates that differed by policy-relevant margins, which the authors interpret as estimates of bias. Although the authors identified several study design factors associated with smaller discrepancies, no combination of factors would consistently eliminate discrepancies. Even with a large number of impact estimates, the positive and negative bias estimates did not always cancel each other out. Thus, it was difficult to identify an aggregation strategy that consistently removed bias while answering a focused question about earnings impacts of a program. They conclude that although the empirical evidence from this literature can be used in the context of training and welfare programs to improve NX research designs, it cannot on its own justify the use of such designs.

To assess nonexperimental (NX) evaluation methods in the context of welfare, job training, & employment services programs, the authors reexamined the results of twelve case studies intended to replicate impact estimates from an experimental evaluation by using NX methods. They found that the NX methods sometimes came close to replicating experimentally derived results but often produced estimates that differed by policy relevant margins, which the authors interpret as estimates of bias. Although the authors identified several study design factors associated with smaller discrepancies, no combination of factors would consistently eliminate discrepancies. Even with a large number of impact estimates, the positive & negative bias estimates did not always cancel each other out. Thus, it was difficult to identify an aggregation strategy that consistently removed bias while answering a focused question about earnings impacts of a program. They conclude that although the empirical evidence from this literature can be used in the context of training & welfare programs to improve NX research designs, it cannot on its own justify the use of such designs. [Copyright 2003 Sage Publications, Inc.]

Mixing across racial and ethnic lines could spur understanding or inflame tensions between groups. We find that white students at a large state university randomly assigned African American roommates in their first year were more likely to endorse affirmative action and view a diverse student body as essential for a high-quality education. They were also more likely to say they have more personal contact with, and interact more comfortably with, members of minority groups. Although sample sizes are too small to provide definitive evidence, these results suggest students become more empathetic with the social groups to which their roommates belong.