Bergmann's rule (named after German biologist Carl Bergmann) is an ecogeographical rule that states that within a species, specimens will tend to be larger if they are from cooler climates or more extreme latitudes. A Cal Poly biology graduate student investigated whether Bergmann's rule applies to the golden mantled squirrel in California. The student measured the body lengths (mm) of 18 squirrels from the following four California locations: Loop Hill (41.7 N), Susanville (40.4 N), Big Bear Lake (34.2 N), and Hemet (33.7 N). The summary statistics are shown in the following table, and the data are shown in the dot plots. Location Sample size Sample mean (mm) Sample SD (mm) Loop Hill 4 281 7.874 Susanville 5 262 10.7 Big Bear Lake 4 253 21.087 Hemet 5 251.6 7.893 Using the summary statistics given, compute the Mean Group Diff statistic