This dissertation consists of two essays on developing new methods for testing the Arbitrage Pricing Theory (APT) and the Present Value Model (PVM), and one essay on correcting heteroskedasticity and cross-sectional correlation in panel study by using the Newey-West Adjustment Matrix. In the first essay, I develop an autoregressive method for testing the APT. Unlike methods currently being used in the literature, this method does not require prior estimation of factor loadings and risk premia. The new methodology is based on the observation that past returns of an asset carry information...