Table 1 Summary of statistical methods used for the psychometric evaluation of the QoR-15NL scale

Construct validity

  Correlation

Spearman's rho

rs

moderate

0.40—0.69

strong

0.70—0.89

very strong

0.90—1.00

Reliability

  Internal concistensy

Crohnbach's alpha

good

0.70—0.90

Split-half reliability

unaccaptable

 < 0.70

fair

0.70—0.79

good

0.80—0.89

excellent

 ≥ 0.90

Responsiveness

Cohen's effect size

large

 ≥ 0.8

Standardised response mean

SRM

large

 ≥ 0.8

Reproducibility

  Agreement

Individual smallest detectible change

SDC

good

SDC < minimal clinically

important difference

  Test–retest reliability

intraclass correlation coefficient

ICC

good

 > 0.7

(two-way random effect model)

Clinical feasibility

  Floor effect

Percentage of patients with

present

if > 15%

lowest possible score

  Ceiling effect

Percentage of patients with

present

if > 15%

highest posible score