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Regression Discontinuity - Institute for Policy Research

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Functional Form: Interactions<br />

• Sometimes the treatment works better <strong>for</strong> some<br />

people than <strong>for</strong> others<br />

– For example, it is common to find that more advantaged<br />

children (higher SES, higher pretest achievement scores)<br />

benefit more from treatment than do less advantaged<br />

children.<br />

• If this interaction (between the assignment variable<br />

and treatment) is not modeled correctly, a false<br />

discontinuity will appear:

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