The data in Table 6.36 are wheat yields for experimental plots having received the indicated amounts of nitrogen. Determinewhether a linear or quadratic trend may be used to describe the relationship of yield to amount of nitrogen.

Table 6.36 Data for Exercise 10 Nitrogen 40 80 120 160 200 240 42 45 46 49 50 46 41 45 48 45 44 45 40 44 46 43 45 45 LO.1