Typicality of Level Change (TLC) as an Additional Effect Measure to NAP and Tau-U in Single Case Research.
Add TLC to your single-case toolbox when data are sparse.
01Research in Context
What this study did
Landman et al. (2024) built a new tool called TLC. TLC stands for Typicality of Level Change.
They made it for tiny single-case graphs where NAP or Tau-U can struggle.
The paper shows how to add TLC to your usual NAP and Tau-U reports.
What they found
TLC gives a second, clearer picture of level change when data points are few.
It does not replace NAP or Tau-U. It sits beside them like a friend.
The authors give step-by-step code so you can run TLC in minutes.
How this fits with other research
Falligant et al. (2022) tested older visual aids like conservative dual-criteria. TLC is the next step: a number, not just a line.
McCauley et al. (2018) asked for higher standards in single-case work. TLC answers that call by tightening effect-size talk.
Cashon et al. (2013) used fancy stats (HLM) to find hidden change. TLC does a similar job with a much lighter math load.
Why it matters
If you run single-case graphs with five or six points per phase, run TLC alongside NAP and Tau-U. It takes one extra column in Excel and gives families a clearer picture of change. Share all three numbers in your report and watch team meetings move faster.
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02At a glance
03Original abstract
Single case research is a viable way to obtain evidence for social and psychological interventions on an individual level. Across single case research studies various analysis strategies are employed, varying from visual analysis to the calculation of effect sizes. To calculate effect sizes in studies with few measurements per time period (<40 data points with a minimum of five data points in each phase), non-parametric indices such as Nonoverlap of All Pairs (NAP) and Tau-U are recommended. However, both indices have restrictions. This article discusses the restrictions of NAP and Tau-U and presents the description, calculation, and benefits of an additional effect size, called the Typicality of Level Change (TLC) index. In comparison to NAP and Tau-U, the TLC index is more aligned to visual analysis, not restricted by a ceiling effect, and does not overcompensate for problematic trends in data. The TLC index is also sensitive to the typicality of an effect. TLC is an important addition to ease the restrictions of current nonoverlap methods when comparing effect sizes between cases and studies.
Behavior modification, 2024 · doi:10.1177/01454455231190741