Our finding of a single second-order factor for the SF-36 data is consistent with other published studies.
Earlier studies have also found support for a one second-order factor for the SF-36 [ 78, 79].
Therefore, various authors have proposed an alternative higher order factor structure of the CES-D [ 1, 11], in which the four first-order factors are considered to be dependent on a single second-order factor for depression.
The results from the factor analyses (both Exploratory Factor Analyses and Confirmatory Factor Analyses) show good support for the proposed structure together with an overall higher-order factor for each scale of the measure.
For example, in a study of 339 patients with Parkinson's disease, confirmatory factor analysis demonstrated evidence to support a single second-order factor for the SF-36 data but did not find evidence to support two second-order factors for physical and mental health components [ 77].
Although the two-factor model fit the data well, we also tested a three-factor model that consisted of a single second-order factor for the KDCS and two second-order factors, representing the physical and mental component summary scores of the SF-36 [ 40].
Confirmatory factor analysis provides evidence supporting a second order factor solution for four subscales and a total IPAQ score.
The CFA provide evidence supporting a second order factor solution for four subscales (preparing the pen, setting the dose, injecting the medicine and maintaining the pen) and a total score (total IPAQ score).
According to the variable importance in the projection (VIP) values, the dominant first-order factors for the nitrate concentration were as follows: the areal percentages of agricultural, forest and residential areas; followed by the slope; the largest patch index (LPI); the flow path gradient (FPG); the slope gradient variance (SGV); and the splitting index (SPLIT).
Our second-order factor model requires the item to factor mapping established for the first-order factors, for its definition, since it is the second-order (more general) factor that is proposed as the explanation for the association among environmental mastery (E), personal growth (G), purpose in life (P), and self-acceptance (S).
