Example 5.15 described a study that involved substituting sunflower meal for a portion of the usual diet of farm-raised sea breams (Aquaculture [2007]: 528€“534). This paper also gave data on y = feed intake (in grams per 100 grams of fish per day) and x = percentage sunflower meal in the diet (read from a graph in the paper).

A scatterplot of these data is curved and the pattern in the plot resembles a quadratic curve.
a. Using a statistical software package or a graphing calculator, find the equation of the least-squares quadratic curve that can be used to describe the relationship between percentage sunflower meal and feed intake. y^ = 0.866 2 0.008x 1 0.0004x2
b. Use the least-squares equation from Part (a) to predict feed intake for fish fed a diet that included 20% sunflower meal.

x 0 6 12 824 30 36 y 0.86 0.84 0.82 0.86 0.87 1.00 1.09