ABSTRACT

The difference between groups in their random slopes is frequently examined in latent growth modeling to evaluate treatment efficacy. However, when end centering is used for model parameterization with a randomized design, the difference in the random intercepts is the model-estimated mean difference between the groups at the end of the study, which has the same expected value as the product of the coefficient for the slope difference and study duration. A Monte Carlo study found that (a) the statistical power to detect the treatment effect was greater when determined from the intercept instead of the slope difference, and (b) the standard error of the model-estimated mean difference was smaller when obtained from the intercept difference. Investigators may reduce Type II errors by comparing groups in random intercepts instead of random slopes to test treatment effects, and should therefore conduct power assessments using end centering to detect each difference.

摘要

在潜在生长模型中经常检查组之间随机斜率的差异，以评估治疗效果。然而，当末端中心用于随机设计的模型参数化时，随机截距的差异是研究结束时模型估计的组之间的平均差异，它与系数的乘积具有相同的期望值对于斜率差异和研究持续时间。Monte Carlo 研究发现 (a) 当根据截距而不是斜率差异确定时，检测治疗效果的统计功效更大，以及 (b) 从截距差。