8 XXX : ButtSharpies

First glance I completely read the graph wrong; "HOLY SHIT, 1 person fit 83 sharpies....."
This post led me to Google "Diameter of a sharpie" (about 11mm, although I couldn't find anything more exact.) And "Number of circles in a circle" Which brought me here: http://www.engineeringtoolbox.com/smaller-circles-in-larger-circle-d_1849.html Where you can determine that in order to get 15 Sharpies in, you have to stretch to a 51mm (2.0") diameter. Also, interestingly, you only have to go to 52mm to get that 16th Sharpie in.
/r/dataisbeautiful
Interestingly users clearly felt less inclined to insert an odd number of sharpies. Most interesting.
These data appear to follow an Erlang distribution rather than a normal distribution, so the *median* value is probably a better estimator.
I took out the part of the posts with only one according to your data and the mean rose to ~5.2 or just 5. So the 2 to 15 total was 91 and the number of butt sharpies between all the cheeks was 471, so 471÷91 is ~5.2.
Request for 16