The graphic shows the average response times for items according to their position in the test sequence and their difficulty (i.e., proportion of correct responses). The visual here answers the following research questions: 1) “Is there a general downward trend in mean item response times toward the end of the test, controlling for item difficulty?” and 2) “Do items become more difficult at the end of the test?” The plot shows data from multiple 60‐item modules on a high‐stakes certification exam. This graph was generated using the R package ggplot2 (Wickham, 2009), and code is available upon request. The solid black line is the grand mean response time by item position across all modules.

First, as indicated by the solid black line, it does not appear that item response times are generally decreasing toward the end of the test, indicating that examinees are not “speeding up” as they reach the time limit. Second, the colored lines, indicating the trends in average response time by position as a function of item difficulty, show that more difficult items take more time to complete than easier items, but this relationship does not depend on item position. That is, items do not become more difficult if placed at the end of the test. Overall, the graphic suggests this exam is not speeded.

该图根据项目在测试序列中的位置及其难度（即正确响应的比例）显示了项目的平均响应时间。此处的图像回答了以下研究问题：1）“在测试结束时，平均项目响应时间是否存在总体下降趋势，从而控制了项目难度？” 和2）“测试结束后，项目变得更加困难吗？” 该图显示了高风险认证考试中来自多个60个项目模块的数据。该图是使用R包ggplot2（Wickham，2009）生成的，可根据要求提供代码。黑色实线是所有模块中按项目位置的平均响应时间。

首先，如黑色实线所示，似乎在测试快结束时，项目响应时间通常不会减少，这表明考生在达到时间限制时并未“加快”速度。其次，彩色线表示按位置平均响应时间随物品难度变化的趋势，表明较难物品比容易物品花费更多的时间来完成，但是这种关系并不取决于物品位置。也就是说，如果放置在测试的末尾，项目不会变得更加困难。总体而言，该图表明该考试没有加速。