The battle between optimization and curve-fitting

In a recent interview with Managing Editor Dan Collins, legendary trader William Eckhardt talked about the battle between optimization and curve fitting. While you always hope your great idea will lead to a winning system, how you select data to test that system can equally lead to success or failure. The excerpt below is from William Eckhardt: The man who launched 1,000 systems. Bill Eckhardt: By trying to improve your system you can make it worse. You can over-fit to past data or maybe just do something that is statistically invalid.