The Effect of Serial Dependence on Visual Judgment of Single-Case Charts: An Addendum

Abstract

This study reanalyzed data presented in a previous investigation (Ottenbacher, 1986a) that explored the relationship between graphic characteristics and visual judgments in single-case charts. Specifically, Ottenbacher computed autocorrelation coefficients for five graphs and examined the relationship between serial dependence and rater agreement or disagreement. The method used by Ottenbacher (1986a) was adopted from previous research and involved analyzing data points combined across baseline and treatment phases. The argument is made that this analysis is incorrect and that serial dependence should be computed using only the baseline data. Reanalysis of the data presented by the previous investigation reveals a strong association (.94) between degree of serial dependence and rater disagreement. The concept of serial dependence and its influence on the analysis of single-case graphs is discussed and the appropriate method of computing serial dependence is presented.

Keywords

single-case design visual analysis serial dependence autocorrelation

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