I am having a problem with understanding some slope data. I downloaded ned 10 and ned 30 and created a 10m and 30m mosaic of my study area using mosaic to new raster. I then used those mosaics to derive the slope of my study area. I then use the Extract by Mask tool to find the slope around two points of interest for various distances up to 25 kilometers. So far, so good the output looks fine. However, as the mask distances get larger and as the areas begin to overlap it seems that the average of the values of slope from the ned 30 and ned 10 should trend toward an average. Instead, they get wildly different. That has me perplexed, so I hope someone might have a suggestion or could point me to a resource to help me understand what could be causing this variation. Many thanks.