Hi there,

I have two sets of data:
1. Concentration of a nutrient in water
2. Cell densities of an organism taking up this nutrient

The two sets are inversely related as cell densities increase with reduced nutrients. My goal is to define the relationship between these sets with a regression analysis. When I use the built in Excel regression data analysis tool, the result is a fairly well fitted model (R^2 = 0.89). Now, the provided residual plot gives an estimated model which is far from linear. This is good, but I don't understand how Excel calculates a higher-order plot with just two coefficients (intercept and slope)? Help is very much appreciated!

Thanks folks!