Regression Discontinuity - Institute for Policy Research
Regression Discontinuity - Institute for Policy Research
Regression Discontinuity - Institute for Policy Research
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Fallible RD?<br />
• When we probed the New Jersey data, we found that the<br />
discontinuity in the McCrary test was driven by cases with a<br />
September 1 st cutoff.<br />
• Five years ago, children who were born on September 1 st<br />
were born on a Monday and children who were born on<br />
August 31 st , were born on Sunday.<br />
• Birth record data shows that there are large “day” effects<br />
(i.e. more births on Fridays and Mondays, fewer births on<br />
weekends and holidays), so the discontinuity may be driven<br />
by day effects<br />
• Not a problem if the “day effects” are not correlated with<br />
students’ achievement, but still under investigation.<br />
• Not a problem in 4 other states.