Origin Ver. and Service Release (Select Help-->About Origin): Origin Pro 8.5 Operating System:windows 7 professional HI, I am running an experiment and I want to operate Whitney - Mann test in order to compare the mean values of two uneven groups. The groups are men and women and I have calculate their mean value and I want to see if there is a difference between them. I have my data in two columns. One for the mean values and one for showing if this value is for men or women by putting the letter a for men and b for women. I saw a video on origin and I follow the same procedure but it doesn't work and I get the follow message: Unknown error; function return error code: - 11. What could be the problem? I also tried the (NPH) two independent samples and i get the same message.