This indicates that the ICU-level random intercepts are representing unexplained differences between ICUs, whereas differences between-years within-ICUs are similar across sites.
However, in that study, variations in exposure both between city and between years within city contributed to the exposure gradient.
Phenotypic correlations between traits within years and between years within traits were determined using the non-parametric Spearman correlation coefficient.
Besides, for the comparison between years within one country as well, we should take account of differences in the number of potential donors each year.
To assess the variation in longitudinal distribution between years within each movement pattern, we calculated a coefficient of variation (CV).
The level-two (ICU-year, or between years within ICUs) random effects are assumed to be independently normally distributed with variance σ IY 2, independently of the level-three random effects.
Hierarchical models are also known as multilevel models and the three levels of the hierarchy are: between ICUs (level three), between years within ICUs (level two, treating years as independent random effects, which we refer to as ICU-years) and between patients within ICU-years within ICUs (level one).
Variation in incidence between countries may partly reflect different sensitivities and specificities of national surveillance systems, whereas variation between years within countries is more likely to be a true reflection of the well-known irregular fluctuations in meningitis incidence across the meningitis belt [ 1].
Genotypic frequencies changed significantly between years within year class (Table 5).
