Regression Discontinuity - Institute for Policy Research
Regression Discontinuity - Institute for Policy Research
Regression Discontinuity - Institute for Policy Research
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Potential Issues with using<br />
Age-Related Cutoffs<br />
• The <strong>for</strong>egoing concerns suggest null hypotheses we could examine:<br />
– Since treatment children had opportunities to attrite that control children did<br />
not have, there should be more “missing” children in the treatment group.<br />
• Examine the data to determine whether there is a discontinuity in the<br />
DENSITY of observations at the cutoff.<br />
– Attrition could result in compositional differences between groups<br />
• Examine the data to determine whether there are discontinuities in third<br />
variables CONDITIONAL MEANS at the cutoff<br />
• Both of these concern possible violations to the RD assumption of no<br />
discontinuities in the potential outcomes (called Assumption 2)<br />
• Begin with conditional means on 3 rd variables