. In this case, the circleis expected to rest at equilibrium with its center of mass at the origin. However, if,for example, the data come from a population that follows an annual sinusoidal patternwith peak in January and trough in July, then, as compared to the other observedfrequencies, Nj,1 should be large or heavy, and Nj,7 should be small or light. Consequently,in this case, the circle will incline in the direction of January, and its centerof mass move away from the origin in the direction of the excess weight. Viewed this way, the test assesses whether the distance from the expected center of mass at (0, 0) to the observed center of mass is significantly large.