Overall and differential attrition — attrition • baselinr

Computes overall and differential sample attrition for a two-group design, the inputs to the What Works Clearinghouse (WWC) attrition standard. Differential attrition is the absolute difference between the treatment and comparison attrition rates.

Usage

attrition(treatment, retained, na.rm = TRUE)

Arguments

treatment: Vector identifying group membership; exactly two unique non-missing values (the larger is treated as the treatment group, as in hedges_g()).
retained: Logical (or 0/1) the same length as treatment: TRUE/1 for cases retained in the analytic sample, FALSE/0 for those lost.
na.rm: Logical; drop rows where treatment or retained is NA. Default TRUE.

Value

A one-row data frame with columns attrition_overall, attrition_treatment, attrition_comparison, and differential_attrition (all proportions).

Details

This function reports the attrition rates; it does not classify them. Compare the overall and differential rates against the WWC attrition boundary for your chosen response assumption (cautious or optimistic) in the Procedures Handbook.

References

What Works Clearinghouse (2022). Procedures Handbook (Version 5.0). U.S. Department of Education.

Examples

set.seed(1)
g <- rep(c(1, 0), each = 100)
kept <- rbinom(200, 1, ifelse(g == 1, 0.9, 0.8))
attrition(g, kept)
#>   attrition_overall attrition_treatment attrition_comparison
#> 1              0.12                0.06                 0.18
#>   differential_attrition
#> 1                   0.12