Table 1 Testing and statistical methods of psychometric testing and diagnostic accuracy test

Reliability

 Internal consistency

Cronbach’s method

Cronbach’s α statistic, > 0.7 = satisfactory

All 350 older people

 Stability

Two-week test-retest reliability

Intra-class correlation coefficient (ICC), >  0.75 = satisfactory

A subgroup of at least 50 older people (Giraudeau & Mary, 2001)

Validity

 Criterion-related validity

Concurrent validity: correlating GFI-C with the Fried’s frailty phenotype

Pearson moment–product correlation coefficient, r ≥ 0.7 & < 0.9 = satisfactory

All 350 older people

 Construct validity

 1. Known-groups method

Comparing the GFI-C of older people in the community and long term care facility

1. Independent sample t-test, significant result = satisfactory

All 350 older people

 2. Hypothesis testing:

Correlating the frailty (GFI-C) with cognitive level (AMT) and physical ability (SBI)

2. Pearson moment-product correlation coefficient, r > 0.5 = satisfactory

All 350 older people

 3. Factor analysis

3. Confirmatory factor analysis

χ²/df < 5.0, TLI > 0.90, CFI > 0.90,

GFI > 0.90, RMR < 0.05, RMSEA ≤ 0.08.

All 350 older people

Diagnostic accuracy test

 Sensitivity and specificity analysis

Comparing GFI-C results with the Fried’s frailty phenotype results

The receiver-operating characteristic (ROC) curve, sensitivity and specificity > 0.70

All 350 older people

 Discriminative properties of the diagnostic accuracy

The area under the curve (AUC), AUC > 0.70