Missing-Data on The Standard Errorhttps://jongha-jeon-dev.github.io/standarderror/tags/missing-data/Recent content in Missing-Data on The Standard ErrorHugo -- 0.123.7en-gbTue, 13 Oct 2026 00:00:00 +0000Linear Algebra 3: Your Covariance Matrix Is Not Positive Definitehttps://jongha-jeon-dev.github.io/standarderror/lectures/linear-algebra-3-positive-definite/Thu, 27 Aug 2026 00:00:00 +0000https://jongha-jeon-dev.github.io/standarderror/lectures/linear-algebra-3-positive-definite/Three correlations, each one a defensible estimate, each one inside [-1, 1] — and together a claim that a particular portfolio has a variance of minus 0.11.ML 38: A Missing Value Is Information, Until the Process Behind It Changeshttps://jongha-jeon-dev.github.io/standarderror/lectures/ml-38-missing/Tue, 13 Oct 2026 00:00:00 +0000https://jongha-jeon-dev.github.io/standarderror/lectures/ml-38-missing/Imputation treats a gap as a lost number. Sometimes the gap is a record of a decision, worth more than the number, and the model that uses it depends on the decision staying the same.