Table 6.

Summary of rating scale diagnostics

Category	Observed count (%)	Expected score measure	Average measure	Threshold	Infit MnSQ	Outfit MnSQ
0 = Not at all	11205 (49.1)	−4.22	−4.24	-	1.03	1.00
1 = Several days	8480 (37.1)	−2.12	−2.12	−3.43	0.94	0.90
2 = More than half the days	2338 (10.2)	0.41	0.60	0.48	0.94	0.94
3 = Nearly every day	804 (3.5)	2.57	2.33	2.95	1.27	1.35

MnSQ Mean square, Zstd Standardised scoreρ: Spearman’s correlation coefficient; ^aInfit mean square value should range from 0.6 to 1.4, closer to 1 indicates better fit; ^bOutfit mean square value should range from 0.5 to 1.7, closer to 1 indicates better fit. ^cSpearman’s correlation between item and total score