Data sgp is an analytics package that utilizes longitudinal student data to produce statistical growth plots (SGPs). An SGP measures a students current test score by comparing it to their prior performance and estimates of their ability (their academic peers) using a series of windows. This allows for a more accurate measure of students achievement than unadjusted test scores, as well as a fuller picture of the students achievement journey by including previous and future performance.
The SGP package provides both lower level functions that do the calculations and higher level wrappers for those functions. For basic analyses, the lower level functions require WIDE formatted data whereas the higher level function require LONG data. If your data is in a different format than the recommended formats, there are several workarounds provided by the SGP package that can be used to calculate an SGP. Refer to the SGP data analysis vignette for detailed examples and documentation on how to use this tool.
A key element of the SGP methodology is its ability to stipulate a target or goal for a students achievement in the form of a growth standard. By calculating and establishing the target using SGP, it is then possible to compare and report students progress towards their target goal in a metric that is meaningful and informative to stakeholders.
SGPs are estimated from a students standardized test score history and may suffer from large estimation errors. As such, the resulting SGPs can be noisy measures of the latent achievement traits underlying these scores. However, the unique feature of SGPs is their ability to provide a statistical estimate of what a student needs to do to reach their goal by comparing the students current performance to the estimated prior performance of their academic peers.
For example, if a student has a SGP score of 75, this indicates that they need to score above the 75th percentile of their academic peers in order to reach their target achievement. This allows teachers and administrators to quickly determine whether a student has made progress toward their goal or not.
In addition to the window specific SGP, SGP also includes a current SGP which provides the most recent measure of student growth for a given student. The current SGP can be useful to teachers as a quick check in on a students progress, and it can also be used to inform instructional decisions.
To ensure the accuracy of the results, SGP uses a set of assumptions to compute the students growth. These assumptions are based on the fact that student progress in mathematics and ELA is measured by the difference between their current test score and their past performance. For students in grades 4 through 8, SGPs are calculated by comparing their current test score to the previous year’s grade level assessment. SGPs are not calculated for science because MCAS tests are only administered in grades 5 and 8. In addition, SGPs are not calculated for students in grade 10 because the students are compared to their previous 10th grade test score instead of their previous 9th grade test score.