Free public beta until December 4, 2026: every course is open, no card needed. After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept. How the beta works

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Adjusted R-Squared & ANOVA Identity Sprint

Rescale R^2 for an added predictor, or complete the SST=SSB+SSW split -- two chapters' own variance-accounting identities.

⏱️ 75s

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