I am using the Directional Distribution (Standard Deviational Ellipse) tool under the Spatial Statistics toolbox and Measuring Geographic Distribution toolset for an analysis I wish to publish. The results of running the tool looks great but I want to make sure I understand how they were created.
The ArcGIS help website mentions “When the underlying spatial pattern of features is concentrated in the center with fewer features toward the periphery (a spatial normal distribution) a one standard deviation ellipse polygon will cover approximately 68 percent of the features; two standard deviations will contain approximately 95 percent of the features”. The key word in that sentence is “When […]”.
Thank you for all your help,
A figure would help...but a few comments
For mechanics, I am sure you have seen the first, but may have missed the second
PS 5 points?....don't get too excited about those ellipses, they hardly meet conditions for any sort of testing or representation.
I you are interested in the bivariate normal distribution, there is a starting point here
Indeed I had not found some the links you suggested. I'll do some more reading and see if all my questions are answered ;-).
And you are right about the low sample size for some of my ellipses. Thankfully, most have hundreds if not thousand of points.