I am using JMP to find a relationship between drought index values and yearly corn yields for a 30 year period. I have drought data for seven different indeces and each index ranges from -6 (severe drought) to +6 (extremely high precipitation).
The drought data contains monthly drought index values for March-September for every year from 1981 to 2011. The corn yield data contains one number (bushels/acre) for every year from 1981 to 2011. I built two side-by-side graphs in JMP, with one showing corn yield data over the 30 year period and the other showing drought data from one particular index over the same time period. Both are smooth curves and visually line up and seem to have a relationship.
My problem is that I have no idea how JMP is processing the drought data. There are eight separate drought index values per year, every year, for each drought index, and only one value per year for the corn yield data. I assumed that JMP was smoothing out the drought curve by taking an average of the eight index values for every year, then using that number in the graph construction but I haven't been able to find any literature that can tell me this for certain.