What is the role of stock covariance matrix in portfolio optimization? How to measure 1000 stocks’ covariance efficiently(using factor loadings)? What is stationarity?(weak and strong) What is cointegration? In pairs trading, what is the difference between cointegration and correlation? Why can’t we use correlation? Linear Regression assumptions? What is multicollinearity? What are the problems it cause? How to solve it? Explain L1 and L2 regularization. Why is L1 sparse? Which is differentiable? How to solve L1 using numerical methods? Coding: gradient descent to calculate minimum for x**2 - 2*x + 1 + 3 * np.sin(np.pi * x)
