theorem ols_bias_magnitude (covZε varZ₁ varZ₂ : ℝ)
(hvar₁ : 0 < varZ₁) (hvar₂ : 0 < varZ₂)
(hcov : 0 < covZε) (hmore : varZ₁ < varZ₂) :
|simultaneityBias covZε varZ₂| < |simultaneityBias covZε varZ₁| := by
simp only [simultaneityBias, abs_div, abs_of_pos hcov,
abs_of_pos hvar₁, abs_of_pos hvar₂]
exact div_lt_div_of_pos_left hcov hvar₁ hmoreCES Estimation Theory: Connecting Theory to Data