Cross Validated is a good bet. From the site:
Q&A for people interested in statistics, machine learning, data analysis, data mining, and data visualization.
Mathematics also might be a good place for your question - they have a statistics tag there, and your question looks more mathematical, less computer-sciencey. From the tag info:
Mathematical statistics is the study of statistics from a mathematical standpoint, using probability theory and other branches of mathematics such as linear algebra and analysis.
As your question has more of that than the previous quote, it might be the more appropriate site.
EDIT:
Cross Validated also has a tag for mathematical statistics. From the tag info:
Mathematical theory of statistics, concerned with formal definitions and general results. Mathematical statistics is the study of statistics from a mathematical point of view, concerned with formal definitions and general results.
So your question looks equally well suited for both sites.