A trend line is a straight line intersecting a group of data points on a graph; its location and slope are determined through statistical analysis. Once a student has taken at least three Star Reading tests, a trend line can be calculated using the Scaled Scores as data points. The Scaled Score that falls on the trend line at a particular time is the trend score.
A trend score cannot be calculated for a student who has taken two or fewer tests.
Imagine that a student has taken five Star Reading tests since the beginning of the school year. That student's Scaled Scores (blue dots) are shown below, along with the calculated trend line (red).
Less than a month later, the student takes another Star Reading test and gets a Scaled Score of 550, which is a significant jump for such a short period of time; the score from the test prior to this was only a little over 400. The student's teacher evaluates the suggested skills and thinks they are too difficult for the student at this time. It is possible that the student just made several lucky guesses during the most recent test, explaining the unusually large rise in the Scaled Score.
If the teacher chooses to use the trend score when viewing suggested skills, the skills will be based on the score the student would have gotten on that same testing date if the student had continued on the trend line (in this case, 496).
A trend score gives a teacher a way to change the skills suggested for the student if the teacher believes the student's performance on the most recent test was far outside the norm for that student, without the risk of having skills suggested that are too easy or too difficult.