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Regression-Discontinuity Design - Institute for Policy Research

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Addressing Potential Issues with using<br />

Age‐Related Cutoffs<br />

• Differential entrance and attrition time in TR and CO groups<br />

– Because RD study lacks an initial defined sample, cannot assess attrition and<br />

selection effects<br />

– The issue then is: Are there compositional differences between children who<br />

make it to the fall of their kindergarten year (treatment group) and children<br />

who are just starting pre‐K (control group)<br />

• Particularly troubling concern because it could introduce serious bias<br />

in the design and make the approach invalid<br />

– Prompting some critics to ask, Is this an RD design at all?

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