This sentence explains why formulas can get it wrong and cause investors to make wrong and money-losing decisions.

If there was a way for an investor to be 100% certain about the suitability of a formula that he or she uses in order to choose how to invest, then that investor would always be right in his or her predictions, and would always make profit from investing. Have you ever met or heard of such an investor?

This proves that investment formulas are used by investors just to convince themselves to make an investment decision. If you miss crucial information and data when using a formula, this will inevitably lead to making a loss.