In his response, Hankins remarked that both Norman and Wyrwich made too much of his examples, and seemed to have missed his point, which is that Ferguson's δ is an additional index of an instruments' measurement properties, beside reliability, validity and interpretability, and that Ferguson's δ can only be computed on the assumption that the measurement is valid and reliable [ 6].
The McGill Pain Questionnaire was pre-defined as the primary outcome measure, and sample size was calculated to detect a difference of 8 units on the total pain rating index of this instrument after 8 weeks of healing.
This seems to me to miss the point: the examples are to illustrate the utility of Delta as an additional index of an instrument's measurement properties.
The studies of adaptation for these countries clearly presented the stages of translation and semantic adaptation, exploratory and confirmatory factor analysis (CFA), and reliability indices of the instrument, maintaining the five-dimension structure, with good indices of fit and satisfactory internal consistency values (Cronbach's alpha greater than.70).
However, the adequate reliability indices of the instrument in our sample shows that the modifications we made have not diminished the noted satisfactory psychometric characteristics of the Arabic translation of the WHOQOL-Bref in this setting [ 36].
The same clinical indexes and the same type of instruments as in the original study were used.
Appended quarterly to the long-running monthly survey of 500 households that produces the Index of Consumer Sentiment, this instrument inherits the sample design and statistical rigor of that household economic survey.
The degree of comorbidity severity was assessed using the Index of Coexistent Disease (ICED), an instrument that has been validated in dialysis populations [ 21].
Reproducibility for the Index of Eating Difficulty, an instrument developed in China, was reported to be 0.99, and the weighted kappa for test-retest reliability was reported to be 0.89 [ 34].
Did investigators use instruments that yield a single indicator or index number, a profile, or a battery of instruments?
This is particularly the case with the introduction of a 3-year lag to the index of diversity which yields valid instruments and statistically significant OLS coefficients.
