Johnny,

Sorry for my delay in replying, was away from my computer earlier this week.

I think backtesting is useful, but not infallible for identifying a good trading method. In your question, it sounded to me as if you were confusing data accuracy with usefulness. I do some backtesting to learn more about what may be significant parameters or conditions to watch. But it is a loose connection, not a hands-off eyes-closed can't-fail trading system.