if p 2 / p 1 > 0.75 {\displaystyle p_{2}/p_{1}>0.75} [15]:5.3.2.2 (at least - standards vary)[17] ϵ = 1 − ( 0.351 + 0.256 β 4 + 0.93 β 8 ) [ 1 − ( p 2 p 1 ) 1 κ ] {\displaystyle \epsilon =1-(0.351+0.256\beta ^{4}+0.93\beta ^{8}){\bigg [}1-{\bigg (}{\frac {p_{2}}{p_{1}}}{\bigg )}^{\frac {1}{\kappa }}{\bigg ]}} [15]