Hi Matthew:

      Thank you very much for sinccere reply! You know I have asked such problems for several times,but your answer is the first reply! Thans a lot! I want to know further

(1)how to define the threshold? Another words the reason for definition of threshold is what?

(2) Is the the range number of colour column is Z statistics?

(3) Only after  I elevate the thrsehold   the two groups comparision reach statstics difference,How to interpret it?

 Couly you help me again,thanks in advance.

All the best!

                                                                                                                                                            Nancy Li