Table 1 Quadrant definitions

Q ₁

{x _i1k ≥a ₁;x _i2k ≥a ₂}

Q ₂

{x _i1k ≥a ₁;x _i2k <a ₂}

Q ₃

{x _i1k <a ₁;x _i2k ≥a ₂}

Q ₄

{x _i1k <a ₁;x _i2k <a ₂}