EDIT: in any case the correct calculation should be http://www.wolframalpha.com/input/?i=%281-%2810^-14%29%29^%2... which gives a 30% chance of failure, versus http://www.wolframalpha.com/input/?i=%281-%2810^-15%29%29^%2... for a 3.5% chance.
I was calculating the expected number of wrong bits per full read of the drive.
You calculated the chance of a perfect read which is similar but not the same.
I thought "of one bit being wrong" said it, but I can see how you misread it. Hopefully people will read the thread and see these replies as well.
EDIT: in any case the correct calculation should be http://www.wolframalpha.com/input/?i=%281-%2810^-14%29%29^%2... which gives a 30% chance of failure, versus http://www.wolframalpha.com/input/?i=%281-%2810^-15%29%29^%2... for a 3.5% chance.