Having trouble figuring out what I am missing about the trendline function as displayed on a scatter plot chart and why using the function does not generate results in line with the R2 value. Here are the details. I have the following data set:
2331 99
2262 96
2259 96
2235 94
2175 87
2163 85
2067 66
2049 62
I scatter plot this data set, and insert a polynomial trendline, displaying the equation on the chart. Results are the function y = -0.0004x2 + 2.0072x - 2253.2 with Rē = 0.9999. Looks promising. However, when I duplicate the function as a formula to get predicted results, my answers are no where close to the original Y values. Instead, I get the following computed Y values for each X:
2331 252.16
2262 240.43
2259 239.83
2235 234.80
2175 220.21
2163 216.95
2067 186.69
2049 180.19
What am I missing? I guess it is possible that I have made a rudimentary mistake, but I have been through it a couple of times and keep getting the same problem...
Bookmarks