Clarification of Odds

From SSH I believe that I have deduced that with 2 cards t o come and drawing to an open ended straight I need to have pot odds of 4.75/1 to break even.
Now, on P94 of Jones' Winning LLH I see an example of such a draw. However, I am confused in that the advice given doesn't seem to take into account pre-flop bets and just tells me to bet taking into account the flop bets, i.e. Jones says that on the flop 2 people call, you raise, bettor makes it 3 and one or two of the others call and we should cap. I understand this but am confused by the fact that Jones seems to ignore the pre-flop bets when he says that since I am getting 2 or 3/1 on the flop bets I should raise.
Am I mis-reading/understanding this or does Jones really ignore the pre flop bets in his calculation?
Which is the correct methodology, pre-flop and flop bets or just flop bets when calculating odds?
Thanks.