ABSTRACT

Student growth percentiles (SGPs) are currently used by several states and school districts to provide information about individual students as well as to evaluate teachers, schools, and school districts. For SGPs to be defensible for these purposes, they should be reliable. In this study, we examine the amount of systematic and random error in SGPs by simulating test scores for four grades and estimating SGPs using one, two, or three conditioning years. The results indicated that, although the amount of systematic error was small to moderate, the amount of random error was substantial, regardless of the number of conditioning years. For example, the standard error of the SGP estimates associated with an SGP value of 56 was 22.2 resulting in a 68% confidence interval that would range from 33.8 to 78.2 when using three conditioning years. The results are consistent with previous research and suggest SGP estimates are too imprecise to be reported for the purpose of understanding students’ progress over time.

摘要

当前，学生成长百分位数（SGP）已被多个州和学区用来提供有关单个学生的信息以及评估老师，学校和学区。为了使SGP在这些目的上具有防御性，它们应该是可靠的。在这项研究中，我们通过模拟四个年级的考试成绩并使用一，二或三个条件年来估算SGP，从而检查了SGP中的系统误差和随机误差。结果表明，尽管系统误差的量很小到中等，但不管调节年限的长短，随机误差的量都很大。例如，与SGP值为56相关联的SGP估计的标准误为22.2，导致68％的置信区间在使用三个条件年时范围从33.8到78.2。