title: Combining nonoverlap and trend for single-case research: Tau-U.
abstract: A new index for analysis of single-case research data was proposed, Tau-U, which combines nonoverlap between phases with trend from within the intervention phase. In addition, it provides the option of controlling undesirable Phase A trend. The derivation of Tau-U from Kendall's Rank Correlation and the Mann-Whitney U test between groups is demonstrated. The equivalence of trend and nonoverlap is also shown, with supportive citations from field leaders. Tau-U calculations are demonstrated for simple AB and ABA designs. Tau-U is then field tested on a sample of 382 published data series. Controlling undesirable Phase A trend caused only a modest change from nonoverlap. The inclusion of Phase B trend yielded more modest results than simple nonoverlap. The Tau-U score distribution did not show the artificial ceiling shown by all other nonoverlap techniques. It performed reasonably well with autocorrelated data. Tau-U shows promise for single-case applications, but further study is desirable.
authors.affiliation: Texas A&M University, College Station, TX 77843, USA. rparker@tamu.edu
authors.forename: Richard I
authors.initials: RI
authors.lastname: Parker
authors.forename: Kimberly J
authors.initials: KJ
authors.lastname: Vannest
authors.forename: John L
authors.initials: JL
authors.lastname: Davis
authors.forename: Stephanie B
authors.initials: SB
authors.lastname: Sauber
mesh_terms: D006801:Humans; D008962:Models, Theoretical; D012107:Research Design; D018709:Statistics, Nonparametric