As compared to the models from Probs. 20.4 and 20.5, a somewhat more sophisticated model that accounts for the effect of both temperature and chloride on dissolved oxygen saturation can be hypothesized as being of the form,
os = α0 + ƒ3(T) + ƒ1(c)
That is, a constant plus a third-order polynomial in temperature and a linear relationship in chloride are assumed to yield superior results. Use the general linear least-squares approach to fit this model to the data in Table P20.3. Use the resulting equation to estimate the dissolved oxygen concentration for a chloride concentration of 10 g/L at T= 20°C.