These courses were useful to understand M2 (Linear Algebra and Complex Integration) and ProbStat, courses provided by BITS Pilani and nearly every other engineering program.

Probabilistic Systems Analysis and Applied Probability - MIT OCW

Statistics 110: Probability - Harvard

Linear Algebra - MIT OCW

Complex Variables with Applications - MIT OCW

Matrix Methods in Data Analysis, Signal Processing, and Machine Learning - MIT OCW

Statistics for Applications - MIT OCW

Circuits and Electronics - MIT OCW