Fair point,
it is possible to note a repeating pattern, then move heaven and earth to explain why Tuesday ought to be moved to Friday - the pattern's always right, so it must be the Universe that got it wrong.
That's probably why I see delta as a useful aid, telling me when to get jumpy if in a trade, rather than as a complete trading system ... I might, I must admit, be under rating Delta there though, whilst I'm pretty convinced Biorythms are a load of horse.
Dave
NB - Substitute any vowel you like in place of the last 'ho'.