Table 1.

Performance measures for the correct assignment of subjects to the groups, based on (i) U-matrix clustering or (ii) on the membership to the clinical “low pain intensity but high life activity interference” group, versus the other subjects, i.e., in both cases a two-group assignment task. For group assignment, decision trees built on psychological parameters and implemented as comprehendible Fast and Frugal Trees were used. The performance was measured (i) using the original data, (ii) data sets constructed to provide a negative control by permuting the original psychological parameters. Results represent the medians (and interquartile ranges in parentheses) of the test performance measures from 1,000 model runs using Bootstrap resampling. The parameters correspond to the performance marker set implemented in the R library “caret” (https://cran.r-project.org/package=caret [58]).

Performance parameter [%]	Psychological parameters		Pain and interference related parameters
	Original data	Permuted data	Original data	Permuted data
Sensitivity, recall	92.9 (85.7–100)	21.4 (0–92.8)	58.3 (33.3–66.7)	41.7 (25–66.7)
Specificity	87.2 (83.5–94.5)	59.6 (41.3–73.4)	63.6 (54.5–82.8)	61.6 (37.4–74.7)
Positive predictive value, precision	48.3 (42.4–64.8)	6.3 (0–20.4)	16.7 (14.3–20)	11.5 (6.7–16.3)
Negative predictive value	99 (98.1–100)	87.7 (81.3–98.9)	92.4 (90.9–93.9)	89.5 85.2–92.4)
F1	63.6 (58.7–71.4)	29.5 (13.7–40)	25.5 (21.6–28.6)	18.5 (11.8–25)
Balanced Accuracy	90.1 (87.1–92.2)	46.8 (29.4–72.5)	60.7 56.1–64.3)	51.3 (41.3–59.2)