Problem: Correct usage of GARCH(1,1) Aim of research: Forecasting volatility/variance. Tools used: Python Instrument: SPX (specifically adjusted close prices) Reference material: On Estimation of GARCH Models with an Application to Nordea Stock Prices (Chao Li, 2007) Note: I have checked almost all the Quant.SE posts discussing GARCH, but I have not seen any of them with the approximate nature of what I'm asking. Description: I am doing a personal research of the historical volatility of stock p