I would specifically need to know your needs. Is it just writing the preface to book or editing and proofreading the entire book. (P.S. - I can write and edit in English language. I am very good at it.)
Furthermore, I very well know a few topics in statistics, viz. Graphs and Charts (line graphs, bar graphs, histograms, candle-stick charts, pie charts, and 2D and 3D cartesian coordinate charts) , Permutations and Combinations, Probability, Measure of central tendencies (mean, median, mode, standard deviation) etc. This would be helpful if you require work in writing, editing or proofreading.
I'll await your communication regarding the type of work and deadline by which you seek the work completed.