Intraclass correlation estimates in a school-based smoking prevention study. Outcome and mediating variables, by sex and ethnicity.
Intraclass correlation estimates in a school-based smoking prevention study. Outcome and mediating variables, by sex and ethnicity.
复制标题
DOI：
10.1093/oxfordjournals.aje.a008945
复制
发表时间：
1996-08
影响因子：
5
通讯作者：
Ohidul Siddiqui;D. Hedeker;B. Flay;F. Hu
中科院分区：
文献类型：
--
作者：
Ohidul Siddiqui;D. Hedeker;B. Flay;F. Hu
大多数以学校为基础的预防吸烟研究采用的设计是，将学校或教室分配到不同的治疗条件，同时对个别学生进行观察。这种设计要求根据学校间方差来评估治疗效果。然而，学校间的方差通常大于将学生单独随机分配到不同条件下所获得的方差。因此，检测处理效果的能力降低了，并且很难检测到重要的处理效果。为了评估潜在的功率损失或计算适当的样本量，研究人员需要对感兴趣的变量的类内相关性进行良好的估计。作者在一项以学校为基础的预防吸烟研究中，使用三水平模型计算了一些常见结果变量的班级内相关性。学生嵌套在教室里，教室嵌套在学校里。作者提出了整个数据集的类内相关性估计，以及按性别和种族分开的相关性估计。它们还说明了在规划未来研究时使用这些估计。
Most school-based smoking prevention studies employ designs in which schools or classrooms are assigned to different treatment conditions while observations are made on individual students. This design requires that the treatment effect be assessed against the between-school variance. However, the between-school variance is usually larger than the variance that would be obtained if students were individually randomized to different conditions. Consequently, the power of the test for a treatment effect is reduced, and it becomes difficult to detect important treatment effects. To assess the potential loss of power or to calculate appropriate sample sizes, investigators need good estimates of the intraclass correlations for the variables of interest. The authors calculated intraclass correlations for some common outcome variables in a school-based smoking prevention study, using a three-level model-i.e., students nested within classrooms and classrooms nested within schools. The authors present the intraclass correlation estimates for the entire data set, as well as separately by sex and ethnicity. They also illustrate the use of these estimates in the planning of future studies.