The variance of the performance of a continuous speech recognition system subjected to replica utterances of the same sentence spoken by the same speaker has been investigated. In an experiment with three different speech recognition systems in three different languages with two different grammar conditions it is shown that the sentence word error rate has a variance that can be described in terms of binomial statistics. The distribution of the measured variance shows a remarkable correspondence to the parameter-free theoretical distribution. It is therefore concluded that for the word error rate of a continuous speech recognition system binomial statistics apply.