Second order construct validity

An important aspect of construct validity is the validation of second-order constructs. T coefficient was used to test whether a second-order construct exists accounting for the variations in its sub-constructs. T coefficient is calculated as the ratio of the Chi-square of the first-order model to the Chi-square of the second-order model and a T coefficient of higher than 0.80 indicates the existence of a second-order construct (Doll et al. 1995). 

To construct the central composite design to estimate the coefficients of the second-order model (equation (14)), usually a fractional factorial design of at least resolution V is used. In this case, if the model is valid, then all of the estimates of the main effect coefficients, p., and the interaction coefficients, p. are imbiased. An alternative to the central composite designs for estimating the coefficients of the second-order model are the Box-Behnken designs or the designs referenced in Section 2.2.5. 

When again a second order model was used for the data it appeared that there still was some lack of fit. Therefore models were constructed which included third order model terms. Further examination of these more complicated models however revealed that there was a much too high collinearity in these models. This means that there are systematical effects in the data which cannot be explained in a completely satisfactory manner. It was decided to use the second order model and to neglect further model complexities. The model validation results of the second order model can be found in Table 6.5. 

In the local region we proceed by constructing a model that contains within its region of validity (in some loose sense) the optimizer. This is the idea behind Newton s method, where we expand the surface to second order in displacements from the current point ... 

In order to be able to access the accuracy of a given computational scheme, Pople and co-workers have constructed the so-called G2 set of data.37 This contains a large number of experimental heats of formation for small molecules, and through comparison with calculated values the deviations are expected to yield valid information about the computational scheme. It shall be added that the molecules contain only first- and second-row atoms and no transition-metal atoms, which does limit the generality of the results. 

To proceed further, we shall use the Lie equations, and hence need an initial approximation for the excess viscosity (valid for small volume fractions) from which estimates of the infinitesimal generators can be constructed. At the present time, very little information of this type exists. Indeed, reliable values are available only for the second- and third-order coefficients V2 and 3 appearing in the viscosity virial expansion... 

Second, the system is testable. One can construct the mixtures in order to evaluate their sensory profile. In that respect a mixture system for odor qualities presents the opportunity for further test and validation, which some other methods do not provide. 

The built of realistic clusters or host-guest nanocomposites require effective experimental tools such as transmission electron microscopy (TEM) images, which illustrate the involved crystalline order both in the core and in the outermost particle siufaces. Second relevant information deals with the experimental vibrational spectra of SiC. The validity of theoretical construction of smaU-size dusters and evaluation of their physical properties should follow the experimental behavior. Also, IR and Raman experiments were performed on the SiC nanopartides and will serve as reference for testing the relevance of the carried out numerical simulations performed. Representative experimental data, required for the initiation of theoretical model, are hereafter reported and consist in morphology and vibrational features of SiC nanopartides. 

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