# Standard Deviation: Can I remove some data?

Discussion created by sasan128 on Nov 24, 2013
Latest reply on Nov 24, 2013 by sasan128
Hi all

Suppose That I have measured property "X" in 16 points of a rigid body. This rigid body is consisted of two different materials. In one of them, property X is around 1, and in the other X is around 5. When I measured X, I found a transition zone of X between material 1 and 2. My matrix is something like this:

X=[1.1 1.08 1.05 0.98 1.02 1.29 1.78 2.34 3.78 4.21 4.78 4.98 5.02 5.09 5.1 5.06]

As you can see my findings are reasonable and I expect low value for standard deviation in materials 1 and 2.
Now, I want to calculate standard deviation of data in material 1 and standard deviation of data in material 2. What should I do with the data of transition region (I mean [1.29 1.78 2.34 3.78 4.21])? If I suppose they are for material 1, the standard deviation in material 1 goes very high; Similarly, if I attribute them to material 2, the standard deviation in material 2 increases. Is there any rule to just neglect the transition data? If yes, could you please provide a reference for that (like a book or article) so that I can include it in my report? Because I can not write down I just neglected them.

Thank you very much