Factorising a quadratic?

simpComp

well, I don't need any measurements below 107 steps!!!

I will look into using a linear model...

thanks for your help

symbolipoint

The ordered pairs shown in your FinalCurve_Obj.jpg image attachment can be plotted onto a cartesian coordinate system, and a best line can be drawn. Any points on the line can be used for finding slope, and several points can be used for finding a y-intercept, an average of these taken, and then this can be used as the best y-intercept. I tried this and found a line to fit as
y=(114/63)x-188

Similar to what you said, near x=148 and x=158, the resulting y deviates about 3 inches from what you expected. Much of the rest of the line is a very good fit.

mfb

Careful with mixing relative and absolute error, the value for 112 steps has a larger relative error.
I agree that 2-3 inch are a reasonable value for a maximal error (not including possible measurement uncertainties), but the relative error can be large for small values in column L.