If the tool is moving during this period, the effectivecenter of measurement will be a certain distance from the point at which the measurement started. This distance is the lag.
如果在记录时间内仪器移动，则测量的有效中心和刚开始的测量点有一定的距离，这一距离就是滞后距离。
3
A new report from the Center for Evaluation and Education Policy at Indiana University examines research into how effective this is.