For the materials with predominantly periodic microstructure, such as textile composites with woven and braided microstructure, some of the above described statistical correlation instruments can be used to evaluate deviations from the periodic trends (Cox et al. 2014).
We present a new 3D cross-correlation instrument that not only allows for static and dynamic scattering experiments with turbid samples but measures at four angles simultaneously.
We expected that treatment satisfaction would be positively correlated with instruments scores [ 26], while the presence of non-specific symptoms was expected to have a negative correlation with instrument scores [ 20].
Given the high correlation between instruments, each of the HRQOL instruments appears acceptable apart from the EQ-VAS which exhibited low correlation with the others.
In addition, the degree of correlation between instruments is used to examine their agreement (convergent validity).
A coefficient of greater than 0.5 or less than -0.5 indicates a strong correlation between instruments, 0.30 to 0.49 or -0.49 to -0.30 a moderate correlation, and values between 0.30 to -0.30 a weak correlation [ 24].
In future studies it may be beneficial to identify and code the major and minor meaningful concepts, since this could assist with developing a priori hypotheses regarding expected correlations between instrument domains.
Correlations between instruments measuring the same construct reflect their concurrent validity.
Convergent validity is demonstrated when there are correlations between instruments that measure similar traits or characteristics (Pasquali, 2007).
Correlations between instruments suggest that they are complementary as they measure different aspects of HRQoL and are used for different purposes.
Correlations between instruments were strong and all changes were in the same direction and of similar magnitude, indicating that all instruments are estimating the same, or a similar, latent trait.
