A related method which reduces bias in a near random bit stream is to take two or more uncorrelated near random bit streams, and exclusive or them together. Let the probability of a bit stream producing a 0 be 1/2 + "e", where −1/2 ≤ "e" ≤ 1/2. Then "e" is the bias of the bitstream. If two uncorrelated bit streams with bias "e" are exclusive-or-ed together, then the bias of the result will be 2"e"2. This may be repeated with more bit streams (see also the Piling-up lemma).