There were several potential sources of correlation within the data set: measurements correlated within subjects, visits, eyes, and circular test pattern (central, mid-, and outer rings around the foveal center).
Exploratory analysis of the potential sources of correlation was performed by fitting the mean model described above, assuming the data were independent and examining the residuals of that model for the various sources of correlation.
This paper presents the findings of a detailed study into the sources of correlation in terrestrial laser scanner self-calibration for a basic additional parameter set.
First, the two treatments are deployed at different levels (community and household) and second, there are two sources of correlation in the outcome: within-community and within-child.
Random effects can also be motivated as an omitted subject-varying covariate, thus they give a potential explanation for the sources of correlation [ 19].
Sources of variability include a wide range of factors in this setting, including within-family and genetic sources of correlation, correlations within geographic regions, similarities among workers at a given farm, and other sources of correlation and clustering (Fleming et al. 1992; McKnight et al. 1996).
It is critical to note that this use of the correlation coefficient encompasses gametic phase disequilibrium as well as other sources of correlation such as epistasis and natural selection.
Because the study design included randomization of samples and thus exposures across labeling reactions, an inferential procedure was necessary that allowed the existence of nonnested sources of correlation (labeling and subject).
For these analyses, two sources of correlation were identified and accounted for in each model: those related to the hospital site the patient was admitted to and those related to the individual physician who cared for the patient.
There are different sources of correlations: anatomical divergence (overlap in the sets of presynaptic neurons), shared variability due to feedback or lateral connections, and stimulus-dependent variability (e.g., changes in level).
