Lena sighed. "That’s not simple. That’s a . Ms. Chen is a star teacher. Her kids were already scoring 15% higher before the software. If her class does better afterward, was it the software or just… Ms. Chen?"
But to be rigorous, she added a and used Huber-White robust standard errors (because monthly scores from the same class aren’t independent — a key point from quasi-experimental guides). quasi-experimentation a guide to design and analysis pdf
Hartley nodded. "So we keep the software, but we train Mr. Abel on it too." Lena sighed
Result: The +7 points was statistically significant (p < .01) and practically meaningful. Lena presented to Hartley: "The software works, but only by 7 points, not the 15-point jump you saw in the raw comparison. The raw difference was inflated by Ms. Chen’s prior excellence." If her class does better afterward, was it
Hartley laughed. "You quasi-people have a workaround for everything."