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Correspondence between Fail-Safe k and Dual-Criteria Methods: Analysis of Data Series Stability

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Abstract

Barnard-Brak, Richman, Little, and Yang (Behaviour Research and Therapy, 102, 8–15, 2018) developed a structured-criteria metric, fail-safe k, which quantifies the stability of data series within single-case experimental designs (SCEDs) using published baseline and treatment data. Fail-safe k suggests the optimal point in time to change phases (e.g., move from Phase B to Phase C, reverse back to Phase A). However, this tool has not been tested with clinical data obtained in the course of care. Thus, the purpose of the current study was to replicate the procedures described by Barnard-Brak et al. with clinical data. We also evaluated the correspondence between the fail-safe k metric with outcomes obtained via dual-criteria and conservative-dual criteria methods, which are empirically supported methods for evaluating data-series trends within SCEDs. Our results provide some degree of support for use of this approach as a research tool with clinical data, in particular when evaluating small or medium treatment effect sizes, but further research is needed before this can be used widely by practitioners.

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Notes

  1. Baseline data from a subset of these individuals were previously analyzed by Falligant et al. (2019).

  2. Independent data collectors calculated interrater agreement by comparing DC/CDC/and FSK results generated via the template with the output recorded by each data recorder. That is, each data collector checked to verify that the other data collector correctly recorded and interpreted results from each analysis. We calculated interrater agreement for 100% of applications—initial results yielded 95% (55 of 58 applications) agreement; after reaching consensus on the remaining three applications, the final agreement for output and interpretation of results across all evaluations was 100%.

  3. See Tarlow and Brossart (2018) for a detailed overview of this method. In essence, a null effect model and experimental effect model are generated from these parameter estimates, both of which produce hypothetical data sets yielding two distributions of time-series data from which the null effect and experimental effect distributions are compared and used to calculate a standardized mean difference effect size (d). Interrupted time series analyses can be implemented in behavior-analytic research and should produce high levels of agreement with visual analysis (see Harrington & Velicer, 2015).

  4. PND reflects the number of sessions within a treatment phase that fall outside of the baseline range (for an overview of PND and related methods, see Wolery et al., 2010; for examples of the application of PND, see Carr et al., 2009, and Sham & Smith, 2014).

  5. Note that the more negative the do value is, the more robust the effect size (because in these cases, behavior should decrease in the B phase relative to the A phase). For example, an effect size of do = -2.0 would be a “larger” effect size than do = -1.5.

  6. This represent the base rate of agreement (i.e., 50%) within the sample.

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Correspondence to Michael P. Kranak.

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The authors wish to acknowledge Lucy Barnard-Brak and David Richman, as well as the editor and reviewers for their helpful comments during preparation of this manuscript.

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Falligant, J.M., Kranak, M.P., Schmidt, J.D. et al. Correspondence between Fail-Safe k and Dual-Criteria Methods: Analysis of Data Series Stability. Perspect Behav Sci 43, 303–319 (2020). https://doi.org/10.1007/s40614-020-00255-x

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