Quadratic

Not necceserilly, e.g. we are using quadratic fit for Bradford determination of protein concentration instead of linear

See entire post

... shouldn't be trying to see what fits better. The model you use should reflect the physical of the system, i.e. light absorbance is linear and not quadratic or logarithmic no matter how good the line fits.

See entire post

... 3319.246 x 10^-15 moles/l (Molecular weight of drug - 337.41 g/mole) Dissociation constant = 0.27 nM, How to calculate the free protein, Above is quadratic equaltion, As the unit dissociation constant of drug is in nM, while that of total protein and total drug is in different units, How to calculate ...

See entire post

As it stands, the data looks either linear, quadratic, or sigmoidal/hyperbolic. But "here's a bet I'll bet youse" to steal a line from E. E. Cummings. I bet there is a mistake in the data points at pH 10 and 12. To check that, unfortunately, ...

See entire post

... a line through the data, other than to prove statistically that the slope cannot be distinguished from zero. If the trend is not linear--say it's quadratic, or multivariate--a simple univariate linear model isn't adequate; a univariate linear model may still be statistically significant, but the ...

See entire post