  A method to quantify the error probability at the Kirchhoff-law-Johnson-noise
(KLJN) secure key exchange is introduced. The types of errors due to
statistical inaccuracies in noise voltage measurements are classified and the
error probability is calculated. The most interesting finding is that the error
probability decays exponentially with the duration of the time window of single
bit exchange. The results indicate that it is feasible to have so small error
probabilities of the exchanged bits that error correction algorithms are not
required. The results are demonstrated with practical considerations.
