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Non-Overlap Measures PND PEM ECL (PEM-T) NAP TauU TauUadj
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Percent Non-overlapping Data (PND)
If anticipating an increase, find the highest data point in the A phase, and then find the percent of the B phase data points that exceed it.
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PND - Concerns 1. Instability Sensitive to Outliers
Sensitive to Number of Baseline Observations
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PND - Concerns 2. Ignores Baseline Trend
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PND - Concerns 3. Ceiling Effect
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PND - Concerns 4. No known sampling distribution
Cannot weight effect sizes based on precision 5. Not comparable to group effect sizes Limits audience
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Alternative Effect Sizes: Nonparametric
A series of other non-overlap effect sizes developed to overcome noted concerns with PND
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Percent Exceeding Median(PEM)
If anticipating an increase, find the median of the A phase, and then find the percent of the B phase data points that exceed it.
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Percent Exceeding Median(PEM)
PND PEM Stable - + 2. Account for Trends 3. Sensitive to Size of Effect 4. Known Sampling Distribution 5. Comparability
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Extended Celeration Line (ECL or PEM-T)
If anticipating an increase, find the celebration line of the A phase, extend it, and then find the percent of the B phase data points that exceed it.
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ECL Stable - + 2. Account for Trends +a 3. Sensitive to Size of Effect
PND PEM ECL Stable - + 2. Account for Trends +a 3. Sensitive to Size of Effect 4. Known Sampling Distribution 5. Comparability aAssuming trend is linear and can be extrapolated
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NAP Each baseline observation can be paired with each intervention phase observation to make n pairs (i.e., n = nA*nB). Count the number of Positive (P), Negative (N), and Tied (T) pairs.
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NAP Stable - + 2. Account for Trends +a 3. Sensitive to Size of Effect
PND PEM ECL NAP Stable - + 2. Account for Trends +a 3. Sensitive to Size of Effect 4. Known Sampling Distribution +b 5. Comparability aAssuming trend is linear and can be extrapolated bAssuming independence
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TauU TauU is closely related to NAP If no ties then
TauU is scaled from -1 to 1
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TauU Stable - + 2. Account for Trends +a
PND PEM ECL NAP TauU Stable - + 2. Account for Trends +a 3. Sensitive to Size of Effect 4. Known Sampling Distribution +b 5. Comparability aAssuming trend is linear and can be extrapolated bAssuming independence
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TauUadj To adjust TauU for baseline trend, each baseline observation can be paired with all later baseline observations (nA*(nA-1)/2). Then compute baseline trend:
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TauUadj cSome technical questions about amount of adjustment Stable -
PND PEM ECL NAP TauU TauUadj Stable - + -c 2. Account for Trends +a +d 3. Sensitive to Size of Effect 4. Known Sampling Distribution +b -e 5. Comparability aAssuming trend is linear and can be extrapolated bAssuming independence CTrend adjustment introduces dependency on baseline length dSome technical questions about the amount of adjustment eTrend adjustment alters sampling distribution
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https://jepusto.shinyapps.io/SCD-effect-sizes/
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https://jepusto.shinyapps.io/SCD-effect-sizes/
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References Ma, H.-H., (2006). An alternative method for quantitative synthesis of single-subject research: Percentage of data points exceeding the median. Behavior Modification, 30, Parker, R. I., Vannest, K. J., & Davis, J. L. (2014). Non-overlap analysis for single-case research. In T. R. Kratochwill & J. R. Levin (Eds.) Single-case intervention research: Methodological and statistical advances. Washington DC: APA. Parker, R. I., Vannest, K. J., & Davis, J. L. (2011). Nine non-overlap techniques for single case research. Behavior Modification, 35, Parker, R. I., Vannest, K. J., Davis, J. L., & Sauber, S (2011). Combining non-overlap and trend for single-case research: Tau-U. Behavior Therapy, 42, Scruggs, T. E., Mastopieri, M. A., & Casto, G. (1987). The quantitative synthesis of single-subject research: Methodology and validation. Remedial and Special Education, 8, Scruggs, T. E., Mastopieri, M. A., & Casto, G. (1987). The quantitative synthesis of single-subject research: Methodology and validation. Remedial and Special Education, 8, Wolery, M., Busick, M., Reichow, B., & Barton, E. E. (2010). Comparison of overlap methods for quantitatively synthesizing single-subject data. The Journal of Special Education, 44,
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