In the book this part of the algorithm says p<- probability of adding noise to an element in the vector. Then right next to that it says "Often p = 1" regardless of the fact that in the algorithm pseudocode one line reads "if p >= random number chosen uniformly from 0.0 to 1.0 then". So the p will always be greater or equal to the random number making the probability of of receiving noise effectively 100%. Correct me if I'm wrong, but it seems like the book makes a bad recommendation when it says "Often p = 1". If so it might be worth it to notify the author.