Equation 19 is the result of the analysis of the interaction effect between population and precipitation on maize yields. The interaction model explains about 59% of the variability of maize, which is 4% more than the bilinear regression (≈55%). The model is statistically significant with a p-value of 0.0002088. However, population, precipitation, or the population:precipitation estimate are not statistically significant because their p-values are greater than 5%.