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. Author manuscript; available in PMC: 2022 Oct 1.
Published in final edited form as: Biom J. 2021 Jul 17;63(7):1406–1433. doi: 10.1002/bimj.202000043

Table 3.

Empirical type I, Empirical Power, Coverage for different settings of Extended Cox model compared to Nominal type I error of 5%, Nominal Power of 80% for one-sided test, a =12, f = 12, r = 1, using 10,000 simulations

Relative Time Method (Design parameters and Quantities of Interest) Extended Cox Model: h1t=h0t.expγ0+γ1log(t)
Control arm Shape parameter β0 Effect Size definitions for survival curves Treatment arm Shape β1 calculated via defined effect size Event Size/ Sample Size (Each arm) True HR calculated at tavg=tmed,C+tmed,E2

HR=β1θ0β0β0θ1β1tavgβ1β0
Coverage % for HR at tavg=tmed,C+tmed,E2
using 90% CI:
exp γ^0+γ^1logt±1.645SEγ^0+γ^1log(t)
Coverage % for:

Line 1: log(HR)
at t=1 using
γ^0±1.645.SE(γ^0)

Line 2: β1β0
using γ^1±1.645.SE(γ^1)
Approximation for RT^p calculated at tmed,C using
RT^approxp=β0+γ^1expγ^0β0t^med,Cγ^01/β0+γ^1
Empirical Type I error % Empirical Power %

β0=0.25
RT(p1)=1.52
RT(p2)=1.98
β1=0.2448 601/991 0.8479 90.28% 90.49%
90.27%
4.56% 79.58%
RT(p1)=2.00
RT(p2)=1.50
β1=0.2560 722/1182 0.8984 90.01% 89.86%
89.68%
4.65% 80.16%
β0=0.50 RT(p1)=1.52
RT(p2)=1.98
β1=0.4795 154/216 0.7211 90.05% 89.80%
90.14%
5.18% 78.45%
RT(p1)=2.00
RT(p2)=1.50
β1=0.5247 177/244 0.8054 89.91% 89.83%
90.19%
5.56% 79.88%
β0=0.75 RT(p1)=1.52
RT(p2)=1.98
β1=0.7047 70/87 0.6150 90.27% 90.32%
90.87%
5.49% 76.87%
RT(p1)=2.00
RT(p2)=1.50
β1=0.8064 77/93 0.7202 89.75% 90.00%
90.52%
6.25% 77.41%
β0=1.00 RT(p1)=1.52
RT(p2)=1.98
β1=0.9211 41/46 0.5258 89.58% 90.50%
90.62%
7.00% 77.00%
RT(p1)=2.00
RT(p2)=1.50
β1=1.1029 43/47 0.6423 90.04% 90.57%
90.11%
7.35% 77.75%
β0=1.25 RT(p1)=1.52
RT(p2)=1.98
β1=1.1290 27/29 0.4507 90.00% 90.95%
90.82%
7.31% 75.32%
RT(p1)=2.00
RT(p2)=1.50
β1=1.4150 27/27 0.5712 89.55% 90.79%
90.23%
7.26% 76.11%
β0=1.50 RT(p1)=1.52
RT(p2)=1.98
β1=1.3291 19/20 0.3872 89.52% 92.47%
91.48%
7.89% 74.41%
RT(p1)=2.00
RT(p2)=1.50
β1=1.7440 18/19 0.5064 89.64% 92.58%
90.95%
7.60% 77.09%
β0=2.00 RT(p1)=1.52
RT(p2)=1.98
β1=1.7073 11/12 0.2877 91.41% 94.35%
93.44%
6.65% 70.72%
RT(p1)=2.00
RT(p2)=1.50
β1=2.4586 10/10 0.3938 91.14% 93.37%
92.44%
8.49% 75.58%