I have a question. Thanks a lot for your help, It is about statistics in computing phi correlation coefficient: ( which is a special formula for the Pearson product-moment correlation in the particular case of two binary variable.)
We used the method described in http://www.cmh.edu/stats/definitions/phi.htm See the following contigency table , Y+ Y- ------------- X+ |a11 | a12| ------------ X- |a21 | a22| ----------- Defination of Phi, a11*a22 - a21*a12 phi= --------------------------------------------- sqrt((a11+a12)*(a21+a22)*(a11+a21)*(a12+a22)) phi>0.7 strong correlation. phi>0.3 weak correlation However, there is limitations in this calculation, since if X- is zero, so, a21=0, a22=0; ************************************* There will appear 0/0. (and also big problem in p_value calculation). How to solve this? Is there any other method to quatitfy this when denominator (4 sums) appear 0? ( I think phi correlation coeeficient is not qualified to this situation.) And also compute p value or other statistics term in this situation? . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
