Table 4.

Comparison of Power for Testing {β = 0 or γ = 0}, and βγ + ξ= 0 from the Joint Model

β	γ	ξ	H0: β = 0 or γ = 0			H0: βγ+ ξ= 0
			β Estimate (SE)	γ Estimate (SE)	Power	Estimate (SE)	Power
0.2	0.25	0.05	0.210 (0.056)	0.250 (0.130)	46.6%	0.095 (0.170)	9.7%
0.2	0.15	0.15	0.210 (0.056)	0.149 (0.130)	25.6%	0.176 (0.168)	18.8%

^aThe event time was simulated from an exponential distribution with λ_i(t) = λ₀ exp{βX_i(t)+ξZ_i}, where X_i(t) = θ_0i + θ_1it+ γZ_i and λ₀ = 0.85. To ensure a minimum follow-up time of 0.75 years (9 months) and maximum follow-up time of 2 years, right censoring was generated from a uniform [0.75, 2] distribution. The (θ_0i θ_1i) were assumed to follow a bivariate normal distribution with ${\mu }_{\theta }=\left(\begin{array}{c}0\\ 3\end{array}\right)$ and ${\mathbf{\sum }}_{\theta }=\left(\begin{array}{cc}1.2& 0\\ 0& 0.7\end{array}\right)$.