Tau-U

Calculates the Tau-U index with baseline trend correction (Parker, Vannest, Davis, & Sauber 2011).

Tau_U(
  A_data,
  B_data,
  condition,
  outcome,
  baseline_phase = NULL,
  intervention_phase = NULL,
  improvement = "increase"
)

Arguments

A_data

vector of numeric data for A phase, sorted in order of session number. Missing values are dropped.

B_data

vector of numeric data for B phase. Missing values are dropped.

condition

vector identifying the treatment condition for each observation in the series.

outcome

vector of outcome data for the entire series.

baseline_phase

character string specifying which value of condition corresponds to the baseline phase. Defaults to first observed value of condition.

intervention_phase

character string specifying which value of condition corresponds to the intervention phase. Defaults to second unique value of condition.

improvement

character string indicating direction of improvement. Default is "increase".

Value

Numeric value

Details

Tau-U is an elaboration of the Tau that includes a correction for baseline trend. It is calculated as Kendall's S statistic for the comparison between the phase B data and the phase A data, plus Kendall's S statistic for the A phase observations, scaled by the product of the number of observations in each phase.

Note that A_data must be ordered by session number.

References

Parker, R. I., Vannest, K. J., Davis, J. L., & Sauber, S. B. (2011). Combining nonoverlap and trend for single-case research: Tau-U. Behavior Therapy, 42(2), 284–299. doi:doi:10.1016/j.beth.2010.08.006

Examples

A <- c(20, 20, 26, 25, 22, 23)
B <- c(28, 25, 24, 27, 30, 30, 29)
Tau_U(A_data = A, B_data = B)
#>      ES       Est
#> 1 Tau-U 0.7380952