why is compound symmetry necessary for sphericity? which condition is likely to have sphericity when compound symmetry is present? why is the definition of compound symmetry necessary to establish sphericity? what type of symmetry is necessary to construct a spherical data set? what is the difference between sphericity and compound when sphericity is met does the difference occur? why is compound symmetry sufficient to establish sphericity? why is compound symmetry necessary for sphericity what is compound symmetry what is the difference between sphericity and compound symmetry which term means if compound symmetry is met, then sphericity is also met? why is compound symmetry sufficient to establish sphericity? why is compound symmetry necessary to establish sphericity? why is compound symmetry sufficient to establish sphericity? why is compound symmetry sufficient to establish sphericity when is sphericity sufficient to establish when is compound symmetry sufficient to establish sphericity? does symmetry establish sphericity why is compound symmetry sufficient to establish sphericity why is compound symmetry sufficient to establish sphericity?