Correction on "Helping Theist Arguments" (from 1/3/12)

User efrique on r/atheism has informed me that I made a conceptual error in my article "Helping Theist Arguments". With his permission, I include his comments here without alteration (other than editing out comments not related to his correction, which can be found here.) It's slightly embarrassing for me that I made this conceptual error, given the number of courses I've had on statistics and my background in statistical physics. It's slightly encouraging that efrique ensures me that this is a common mistake, repeated in a number of textbooks.

Doubt & Scientific Certainty

 "Doubt is not a pleasant condition, but certainty is absurd." -- Voltaire (François-Marie Arouet)

My friend Jackie asked me today to explain why I said that I was 99.999% certain there was no God, but not 100% certain. I told her that, as a good scientist, I don't think that we can ever be 100% certain about anything, to which she replied that this doesn't make sense. I sympathise with the fact that she didn't quite understand what I was saying. I think this is a counter intuitive concept for many people and I often see students confused by this idea. Therefore, I thought that I would provide an explanation here as to why I don't think we can ever be 100% certain about almost anything.