Estimating individual health-related quality of life changes in low back pain patients

Table 1 Coefficient of repeatability formulas for p-value < 0.05

Coefficient of repeatability (CR)	Formula
CR₁	2.77 SD₁ \(\sqrt{1-Alpha }\)
CR₂	2.77 SD_1* \(\sqrt{1-Alpha }\)
CR₃	2.77 SD₂ \(\sqrt{1-ICC }\)
CR₄	2.77 SD_2* \(\sqrt{1-ICC }\)
CR₅	2.77 SD₃
CR₆	1.96 SD_2* /\(\sqrt{2}\)

Alpha Internal consistency reliability (Cronbach [4]) or Mosier’s [6] formula for a weighted composite, ICC Intraclass correlation estimated from random effects analysis of variance, SD₁ Standard deviation at baseline, SD_1* Standard deviation at baseline for subgroup reporting “about the same” on retrospective change item, SD₂ Standard deviation of change, SD_2* Standard deviation of change for subgroup reporting “about the same” on retrospective change item, SD₃ Standard deviation of change within subjects over two-time points

ISSN: 1471-2474