Data SGP

The data sgp package provides all of the tools needed to calculate and visualize statistical growth plots (SGP) for individual students. These graphs display their current test score as percentile terms relative to students with similar prior achievement levels; and are widely viewed as more accurate and relevant measures of student progress than unadjusted test scores. Moreover, SGP methodology also offers more insight into how students achieved their current performance by considering impacts such as prior achievement levels or teacher’s effect than simply comparing an unadjusted test score against unadjusted test score comparison.

The SGP methodology establishes latent achievement traits whose estimated values for any given student can be extracted from their past standardized test score history. Unfortunately, estimates may contain large estimation errors; as a result, SGPs estimated may only serve as noisy measures of true latent achievement traits; especially when prior test scores originate in unstandardized assessments with high error variance, such as those contained within the sgpData file described above.

An SGP analysis typically involves two steps: first estimating an estimate of a student’s previous test score, and then comparing their current test score with this estimate of their prior score. This produces an annual growth rate which can be used both to understand and report to stakeholders; in addition, using this methodology allows for setting future growth standards such as how many years will it take them to meet an achievement target.

An SGP would enable stakeholders to determine how many years this will take by showing the expected growth rate relative to current performance and past achievements, and giving an understanding of how much of an increase must occur for their desired result.

SGP methodology not only serves to visualize student growth but can be leveraged as an aggregated measure of educator effectiveness at a school or district level. Interpretations is similar to evaluations; teachers often benefit from receiving individual SGPs so they can use them in self-assessing themselves and hiring processes; this has contributed to its increased adoption globally.

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