Table 1. Criteria for evaluating instruments (14) .

Criteria	Description	Types	Method
Reliability	The degree to which an instrument is consistent or free from random error	• Test-retest reliability • Internal consistency • comparison with proxy responses	• Test–retest reliability (ICC1 and К) • Internal consistency (Coefficient α) • Proxy responses (ICC)
Validity	The degree to which an instrument measures what it intends to measure	• Factorial Structure • Convergent correlations • Discriminant groups	Factorial structure (exploratory or confirmatory factor analysis, Rasch analysis) Discriminant (differences by means or %)
Responsiveness	The ability of instrument to measure important changes following intervention (s)	-	Clinical criteria for change
Item/Instrument bias	Assesses in practical terms if individual questions or summary scores are biased for individuals with SCI2	-	-
Measurement model	Examines if there are problems with floor effects (lowest level of ability) or ceiling effects (highest level of ability).	-	The instrument has scales or measures where 20% of persons with SCI are grouped at scoring determinations. Also, can demonstratesthe score distribution (mean and standard deviation).

¹Intraclass correlation coefficient

²Spinal Cord Injury