The variability due to parameter estimation is of course related to the Markov model order m and to the size k of the alphabet (as we have km+1 parameters for this model) and to the length n of the sequence used for this estimation. For example, considering an order m = 6 model with n = 4639675 (Escherichia coli K12 complete genome) requires to estimate 3 × 46 = 4096 free parameters which results roughly in 400 observation per free parameter. Although this situation seems quite comfortable, we have seen with our simulations that it leads an unacceptable variability for pattern statistics.