Distribution of sentence length of English complex sentences

In previous studies based on many languages, the distributions of sentence length fit several distribution models. Moreover, those research findings are based on a mixture of all kinds of sentences, as the most complex syntactic units, how is the concrete distribution of sentence length of English complex sentences individually? To this end, with the aid of Altmann-Fitter (2013), we analyzed and compared the distribution of sentence length of English complex sentences comprehensively, judging by Brown and LOB corpus, the three research findings were found. Firstly, the frequency distributions of sentence length of English complex sentences well follow the Extended Positive Negative Binomial distribution; secondly, text type or genre could have a significant effect on the distribution of sentence length of English complex sentences; thirdly, there are no any significant differences in the distributions of sentence length of complex sentences between British and American English. The above research findings show that human language is a probabilistic system by nature.