The Correlation. Correlation is a measue of how close the line fits the points that you found in your experiment. Anyone can say whether they think the line is a good fit or not, but to measure it exactly, we use the correlation coefficient: R2.
As the seasons change and the amount of sunlight decreases, less chlorophyll is produced, and the leaves appear less green. Chlorophyll is broken down into simpler compounds at a constant rate, so green leaf color will gradually fade as chlorophyll production slows or stops.
The first factor hinting at early color is the current dryness. I've been up north in the last week, and there are maple trees that have a hint of fall color throughout the tree. It is normal at this time of year to see a colorful branch here and there. But the trees turning now are doing it all over the tree. This leads me to believe that some of the trees may turn color early.