Regression Discontinuity — A Scholarship Cutoff Tale

Apply sharp regression discontinuity design to estimate the causal effect of the Costaria National Merit Scholarship at the 75-point ENAU cutoff. Diagnose naive bias, implement local linear regression with a data-driven bandwidth, and pass the modern referee checklist (McCrary 2008 density test, covariate balance, bandwidth and polynomial-order sensitivity, CCT 2014 robust inference). Closes the four-method credibility-revolution toolkit (Track 2C: FE, IV, DiD, RDD).