WWC attrition model

Research Method · All research methods
Evidence · 1 claim (1 for) · 1 study (1 review), q2 · 0 of 1 report an effect size · 1 claim rests on one study

Description

The WWC attrition model is a framework for limiting attrition bias in assessments of intervention effectiveness: it establishes a standard for acceptable levels of sample attrition in randomized controlled trials by deriving bounds on the bias attrition can induce. The article explains "the WWC attrition model, how that model is used to establish attrition bounds," and notes the standard "may constitute the first use of model-based, empirically supported bounds on attrition bias in the context of a federally sponsored systematic evidence review." The bounds depend on parameter values, most importantly the maximum tolerable bias.

Accounts

• WWC attrition model: model-based, empirically supported bounds on attrition bias in randomized controlled trials: The WWC attrition model is a framework for limiting attrition bias in assessments of intervention effectiveness: it establishes a standard for acceptable levels of sample attrition in randomized controlled trials by deriving bounds on the bias attrition can induce. The article explains "the WWC attrition model, how that model is used to establish attrition bounds," and notes the standard "may constitute the first use of model-based, empirically supported bounds on attrition bias in the context of a federally sponsored systematic evidence review." The bounds depend on parameter values, most importantly the maximum tolerable bias. (John Deke (2017))
• Refining attrition standards through the definition of maximum tolerable bias: The authors recommend that evidence reviews seeking to improve attrition standards direct their efforts at the standard's bias-tolerance parameter rather than at other model inputs. Because their sensitivity analysis shows the attrition boundaries respond most to "the maximum level of bias that an evidence review is willing to tolerate," they conclude that "the most productive refinements to existing attrition standards may be with respect to the definition of 'maximum tolerable bias.'" This makes the tolerance definition the highest-leverage point for adapting standards to new contexts.

Claims

• The Cal-Learn evaluation met WWC evidence standards only with reservations because survey exclusions were based on conditions that could have been affected by the financial incentives [+W]

Related Research Methods

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Key Sources

• John Deke, Hanley Chiang. (2017). The WWC Attrition Standard: Sensitivity to Assumptions and Opportunities for Refining and Adapting to New Contexts. Evaluation Review, vol. 41, issue 2. https://www.mathematica.org/publications/the-wwc-attrition-standard-sensitivity-to-assumptions-and-opportunities-for-refining-and-adapting

Page metadata

Field	Value
type	research-method
id	wwc-attrition-model
title	WWC attrition model
description	The WWC attrition model is a framework for limiting attrition bias in assessments of intervention effectiveness: it establishes a standard for acceptable levels of sample attrition in randomized controlled trials by deriving bounds on the bias attrition can induce.
status	review
moved_from	theory/wwc-attrition-model-bias-bounds, strategy/refine-attrition-standards-via-max-tolerable-bias-definition
generated	by process:sweep-kinds on 2026-10-10
trust	unverified — no one has confirmed this page's content
sources	1 — john-deke-2017

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