I have an independent variable (distance between two stimuli) with 6 levels, but the levels are not equally spaced (e.g. 10, 15, 25, 35, 45, 60 pixels). The distance between two stimuli is important for me (I want to compare the performance in 10 pixels to performance in 60 pixels).
I am confused because I know that ordinal variables are typically non-numeric, and that the differences between points in the scale are not meaningful. But I also know that interval scale is where the differences between points on the scale are measurable and exactly equal.
If the differences between the points were equal, I would think that the variable is on an interval scale, but now I am not sure.
Would this variable be ordinal in this case?