. Author manuscript; available in PMC: 2017 May 1.

Published in final edited form as: Rheum Dis Clin North Am. 2016 Mar 17;42(2):239–252. doi: 10.1016/j.rdc.2016.01.005

Table 1.

Definitions and implications of statistical values for psychometric testing of patient reported measures

Psychometric Property	Definition	Statistics
Reliability-Internal consistency	Measure the relation of the items in a questionnaire to an underlying construct.	Cronbach’s alpha - items are considered to represent a similar construct when alpha is approximately ≥0.7.¹²
Reliability-test–retest or inter/intra-rater	If the questionnaire measures a condition in a reproducible manner.	Intraclass correlation coefficient (ICC). ICC ≥0.7 is considered acceptable for test–retest reliability.³⁹
Validity: Construct	Evaluation of the relationship of an instrument with other instruments.	Correlation coefficient (Pearson’s r, Spearman’s rho). correlation coefficients of >0.50, 0.35–0.50, and <0.35 were considered strong, moderate, and weak, respectively.⁴⁰
Validity: Known groups	Measure of an instrument’s ability to distinguish among different groups (e.g., persons with functional limitation versus those without functional limitation).	T-test or analysis of variance (ANOVA), with post-hoc analysis.
Sensitivity to change	Ability to detect change that exceeds statistical error without regard to clinical relevance.	Effect Size (ES), Standardized Response Mean (SRM), and minimal detectable change (MDC). Larger ES and SRM indicates more sensitivity to change.
Responsiveness	Ability to measure clinically relevant or meaningful change.	Minimal Clinically Important Difference