Archeologists have discovered a rise in shaft graves during the Middle Helladic period in ancient Greece (i.e., around 2000 BC). Shaft graves are named for the beautifully decorated sword shafts that are buried along with the bodies. An analysis of shaft graves was carried out and published in the American Journal of Archaeology (Jan. 2014). The table below gives the number of shafts buried at each of 13 recently discovered grave sites. Construct a dot plot for the data. What number of sword shafts was observed most often in the sample of 13 graves?