Student Attrition Lookup Tool (SALT)
The Student Attrition Lookup Tool (SALT) provides empirical estimates of student mobility rates to help researchers plan for student attrition when conducting studies in U.S. public schools. Student-level, school-based, longitudinal evaluations often encounter study attrition when students move away from, or drop out of, study schools. In some cases, this mobility-induced attrition simply decreases sample size, weakening the study's power to detect a treatment effect. At worst, attrition introduces bias into an otherwise well-designed study and threatens the study's internal and external validity.
Why Use SALT?
With SALT, researchers can get student mobility estimates for different student and school subpopulations and for different transition periods from kindergarten to grade 12. Mobility rates are broken down by three types of mobility that correspond to different types of data collection:
- Left school data: Any move out of the student’s original school (attrition when only collecting data from specific study schools)
- Left district data: Any move out of the student’s original school district (attrition when only collecting data from specific school districts)
- Left state data: Any move out of the state public school system, including moves to a private school or dropping out of high school (attrition when only collecting data from specific states)
SALT can help researchers proactively plan for student attrition during the study design phase. For example, researchers should take student attrition into account when conducting a power analysis. Without good assumptions about student attrition, a study may be underpowered. SALT can also inform decisions about the breadth of data collection efforts. By comparing rates across the three types of mobility, researchers can determine whether, for example, the use of a statewide database rather than a district database will retain enough students in the study to warrant the extra efforts required to secure access to the statewide data.
For an introduction to using SALT and an example of how to use student mobility estimates from SALT in a power analysis, see the SALT User’s Guide.
For details about how we estimated student mobility rates for SALT, see the SALT Technical Supplement.
