Procedures for Calculating SGPs
Damian Betebenner & Adam VanIwaarden
Center for Assessment
June 13th, 2024
Overview & Setup
• The methodology and software used to calculate student growth percentiles is
open source.
• Paper documenting the methodology: Norm- and Criterion-Referenced
Student Growth (2008)
• Calculation of SGPs utilize (the latest versions of) the R software
environment in conjunction with the SGP package that was created and
currently maintained by Dr. Damian Betebenner and Adam VanIwaarden.
• All R source code associated with MA DESE analyses is located on GitHub (no
PII information)
• MCAS: https://github.com/CenterForAssessment/Massachusetts
• WIDA-ACCESS: https://github.com/CenterForAssessment/WIDA_MA
Outline for Calculations
• Calculation of SGPs have always followed the principle that data
cleaning is 90% of the work.
• Step 1: Data preparation: Take raw data files provided by DESE
and create a long formatted .Rdata file suitable for SGP
analyses.
• Step 2: SGP Analysis: Take long formatted .Rdata file from Step
1 and utilize SGP package for analysis.
• Step 3: Post-Processing: Produces state specific formats for the
output
Step 1: Data Preparation
• Source code for data preparation is located (as is all source code) on Github.
• The nomenclature for the names of the source code files is, for example,
Massachusetts_Data_LONG_2024.R to denote the data preparation file for
2024 data.
• Data preparation involves getting naming conventions for variables to align
with the SGP package, making sure variable mode is aligned with SGP
calculations, making sure variable levels are consistent with previous years,
identifying duplicate cases and resolving them.
• For WIDA data preparation, create ACHIEVEMENT_LEVEL (WIDA Level 1,
WIDA Level 2, …) and ACHIEVEMENT_LEVEL_ORIGINAL (1.0, 1.1, …, 2.0, 2.1,
Step 2: Data Analysis - MCAS
• Source code for data analysis is located (as is all source code)
on Github.
• The nomenclature for the names of the source code files is,
for example, Massachusetts_SGP_2024.R to denote the data
analysis file for 2024 data.
• SGP source code specifies the types of norm- and criterion-
referenced SGP analyses to conduct.
Step 2: Data Analysis - MCAS
Massachusetts_SGP <- updateSGP(
Currently, 6 different SGP analyses are
what_sgp_object=Massachusetts_SGP,
conducted:
with_sgp_data=Massachusetts_Data_LONG_2023,
steps=c("prepareSGP", "analyzeSGP", "combineSGP", "outputSGP"),
• Cohort Referenced:
sgp.config=MA_CONFIG,
• Student growth percentiles
sgp.percentiles=TRUE,
• Student growth projections
sgp.projections=TRUE,
• Lagged student growth projections
sgp.projections.lagged=TRUE,
• Baseline Referenced (using pre-
sgp.percentiles.baseline=TRUE,
pandemic growth norms calculated
sgp.projections.baseline=TRUE,
from 2019 and prior data)
sgp.projections.lagged.baseline=TRUE,
• Student growth percentiles
sgp.target.scale.scores=TRUE,
• Student growth projections
save.intermediate.results=FALSE,
• Lagged student growth projections
parallel.config=parallel.config
Step 2: Data Analysis - MCAS
• Some odds and ends of MCAS SGP analyses:
• Due to historical decisions to take advantage of granularity of theta
scores, MCAS SGP analyses currently utilize student theta values
instead of scaled scores.
• Projections and lagged projections are calculated originally in SGP
terms (based upon a 5 year time frame to reach/maintain the
desired level of achievement). Those targets are converted to scale
score targets and utilized by DESE.
• Current targets are calculated and “banked” to be used the
following year (versus using on-time/current norms)
Step 2: Data Analysis - WIDA-ACCESS
• Source code for data analysis is located (as is all source code)
on Github.
• The nomenclature for the names of the source code files is,
for example, WIDA_MA_SGP_2024.R to denote the data
analysis file for 2024 data.
• SGP source code specifies the types of norm- and criterion-
referenced SGP analyses to conduct.
Step 2: Data Analysis - WIDA-ACCESS
WIDA_MA_SGP <- updateSGP(
Currently, 6 different SGP analyses are
WIDA_MA_SGP,
conducted:
WIDA_MA_Data_LONG_2023,
steps=c("prepareSGP", "analyzeSGP", "combineSGP"),
• Cohort Referenced:
sgp.percentiles=TRUE,
• Student growth percentiles
sgp.projections=TRUE,
• Student growth projections
sgp.projections.lagged=TRUE,
• Lagged student growth projections
sgp.percentiles.baseline=TRUE,
• Baseline Referenced (using pre-
sgp.projections.baseline=TRUE,
pandemic growth norms calculated
sgp.projections.lagged.baseline=TRUE,
from 2020 and prior data)
get.cohort.data.info=TRUE,
• Student growth percentiles
sgp.target.scale.scores=TRUE,
• Student growth projections
save.intermediate.results=FALSE,
• Lagged student growth projections
parallel.config=list(BACKEND="PARALLEL", WORKERS=li
PROJECTIONS=4, LAGGED_PROJECTIONS=4, SGP_SCALE_SCORE_TARGETS=
Step 2: Data Analysis - WIDA-ACCESS
• Some odds and ends of WIDA-ACCESS SGP analyses:
• SGP analyses utilize the composite scaled score
• Projections and lagged projections are calculated originally in SGP terms (based
upon a variable year time frame to reach English language proficiency/4.2 level on
WIDA-ACCESS). Those are converted to scale score targets and utilized by DESE.
• Scale score targets are calculated for 1, 2, 3, 4, 5, and 6 year time frames. Based
upon time in MA receiving ELL services, a time-frame is specified.
• Scale-scores are converted back to WIDA-ACCESS achievement levels (1.0, 1.1, 1.2,
…, 2.0, 2.1, …) This conversion is done in a post-processing phase using R source
code provided by https://github.com/CenterForAssessment/WIDA_MA/blob/
master/WIDA_MA_Formatted_Output_2023.R
About this copy
Procedures for Calculating SGPs — MA DESE Procedures, June 13, 2024.
This is an image-based copy of the original Keynote slides; builds and animations are flattened.