TECHNICAL MANUAL
REPORTING ON RELIABILITY & VALIDITY
Construct Validity Construct validity refers to the degree to which an assessment or measurement tool is capable of measuring the attribute (i.e., construct) it is intended to measure. In the case of A2i’s L2M assessment, which is designed to measure student reading ability, correlations with other reading assessments can provide evidence of construct validity. In particular, the convergence between L2M scores and a number of independently administered and validated third-party assessments (see above) provides strong evidence that L2M is measuring the same underlying construct—that is, reading ability. Additionally, because L2M is designed to capture information about student reading ability—a complex trait that includes comprehension, fluency, vocabulary knowledge, etc.—and is correlated with various additional reading assessments, it can be suggested that it is capturing this construct complexity effectively. Predictive Validity Predictive validity describes the extent to which an assessment can predict a student’s future performance. Though individual student growth trajectories frequently differ from one another, the change in each student’s performance over time allows us to make inferences about the rate at which they are growing—a fact that is true only for tests that have equal interval measurements. A2i’s L2M assessment gives scores that are meant to measure a student’s learning progress and are easy to understand. These GE scores are designed to be on a scale where a difference of one point represents one year of learning. As can be seen in the plot below, the growth trajectory of scores from kindergarten to third grade is on an equal interval scale. This attribute of the assessment means that student growth is directly comparable. For example, a student who grew from a beginning-of-year GE of 2.0 to an end-of- year GE of 2.8 (i.e., eight months of growth), would be comparable to a student who grew from a 2.7 to a 3.5 (also eight months of growth). However, for students reading at PreK levels, the progress is faster and follows a curved trajectory.
Figure 6. Equal interval scoring for L2M. The L2M assessment provides scores that are approximately equal interval for the range of reading abilities between the start of kindergarten (Grade GE = 0.0) and the end of the third grade (GE = 3.9). This attribute enables predictive validity such that measuring student growth rates will enable users to effectively predict future student success.
L2M Theta Growth Trajectory
Grade Equivalent Score
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