This video teaches you how to use APT (Arbitrage Pricing Theory) models and formulas. This video shows two specific parts of the APT models the first being the after the fact version and the before the fact version. The before the fact version is focused on as being the most important which is used to calculate expected returns to calculate risk. It is discussed how flexible this model is and how different factors can be moved in and out of the formula and how each different factor is used. To use this on your computer you would need microsoft excel or a similar program. This can really help you when you are investing in a variety of stocks or bonds.