Fit a cubic trend function to the data in Example 2. The orthogonal cubic polynomial is
Example 2
The simplest and most common use of trend analysis occurs when the points t0,,,,,,,, tn can be adjusted so that they are evenly spaced and sum to zero. Fit a quadratic trend function to the data (-2, 3), (-1, 5), (0, 5), (1, 4), and (2, 3).