I won't claim to understand or attempt to explain the math behind the investolution.com charts that predict the overall stock market for the next 40 days.
This page contains the prediction for S&P 500 Index minimum and maximum daily closing prices over the next 40 trading days.
It is predicted that S&P 500 Index will not close under 1,178 and over 1,295 between the dates September 19, 2008 and November 14, 2008. This prediction method was accurate for 71.0% and 95.0% of the cases (for minimum and maximum predictions, respectively) within an error margin of +-5% in the past.
Thanks Andrew for sending in the link.