On one hand, it likely assisted in having enough variance on the risk measure, as twins are more likely to be preterm and of low birth weight.
On the other hand, if we consider Gaussian noise as input that is normally distributed with p̄ as mean value and large enough variance σ, the NMM output results instead in an alternation of quiescent phases and isolated LFP spikes (see Fig. 4), consistent with emergence of Noise-Induced Spiking (NIS) [29].
Hence, this indicator did not show enough variance to be included in the later regression analysis.
To be useful the indicators must, in addition, show enough variance between facilities, have high enough prevalence, and show sensitivity to change when care practices change; 2. Correlating indicators with quality of care.
However the explained variance criteria with a cut-off point of 60% was chosen in order to explain enough variance with as few meaningful factors as possible [ 34, 35].
For principal components analysis, the list of variables and respective factor loadings are presented for the ten fist principal components (PC1 – PC10), which are enough to explain 70.87% of the variance in the original dataset.
The 3 first PCs are enough to explain 52.4% of the variance in the original dataset and the most significant 123 principal components are sufficient to explain 99% of the variance in the original dataset (Additional file 1). Figure 1 Proportion of variance in the descriptor set that is explained by each principal component (for readability the plot was truncated after the fiftieth variable).
Enough principal components to account for over 90%% of the variance in the data were used for the analysis in our previous work [18].
Where the signal is robust enough to be detected in individuals, it allows for the exploration of inter-individual variance in the location of that signal.
Since theoretical values for that number are not reachable, a sufficient number regarding a low enough value of the variance of the results is taken instead (standard deviation will be used instead of variance, in the following).
