Did NetApp's Sep 11 AI-driven earnings beat break it from its storage/memory peers?
Treated: NTAP. Donors: WDC, MU, STX, SNDK (same storage/memory peer group as sndk_supply_glut_fear, with SNDK now a donor instead of a peer input and NTAP promoted to treated). Hand-picked, not algorithmic. Treatment date is NetApp's 2026-09-11 earnings report, an AI-driven beat that pushed the stock as much as +11% intraday before settling to a smaller close-to-close gain. This case was originally planned right after sndk_supply_glut_fear but shelved: as of that writing (a few days post-event) yfinance had zero trading days of post-treatment data, so the post-period gap computed as NaN. Revisited here with a full week of post-earnings data available. **Fails the fit-quality gate** (relative RMSE 1.10x); same outcome as sndk_supply_glut_fear (1.02x): this donor pool cannot reconstruct NTAP's own pre-period path either, so the post-period gap isn't trustworthy in either direction. Shipped as an honest negative result rather than swapped for a better-fitting pool to force a cleaner-looking answer.
Actual vs. synthetic counterfactual
ActualSynthetic (counterfactual)
Fit quality
Fit-window RMSE40.5375
RMSE ÷ fit-window std dev1.10×
Fit-window days128
Confound-window mean gapn/a (fit-end = treatment date)
Post-period mean gap+26.62
Placebo test: same method run on every unit, treated one highlighted
Unit
Mean post-period gap
Max abs. gap
WDC
-51.25%
57.72%
SNDK
+30.61%
44.86%
NTAP (treated)
+26.62%
33.81%
MU
+4.12%
15.23%
STX
-3.15%
10.09%
Verdict
Do not trust the gap below. The fit-window RMSE is 1.10× this unit's own fit-window standard deviation: the donor pool literally cannot reconstruct NTAP's pre-period path at all, which usually means the donor pool is the wrong choice for this unit (e.g. NTAP moved for reasons entirely disconnected from the donors' own drivers), not that a real effect was found. Pick a different/better-correlated donor pool before drawing any conclusion from this run.