Origin Ver. and Service Release (Select Help-->About Origin): OriginPro 8.5.0 SR1 Operating System: win7 Hello, I hope you can help me with the following problem: I have known the errors of y. I got 1st derivative of "y" (dy/dx). Then how to decide the errors of 1st derivative of "y" (dy/dx)? as in the following screenshot: Thanks for your help.