Analysis of multilevel correlation function clearly demonstrated that the threshold level of Hb below which the correlation coefficient rose substantially was 13 g/dl both in BNP and in peak VO2.
Aspatial multilevel models do not consider the correlation of outcomes between areas, only within areas (Auchincloss et al. 2012).
Although construction of a multilevel, spatial correlation model is beyond the scope of this study, several important properties of the populations sufficiently support our assumption of homogeneity.
In a multilevel model we investigated the degree of correlation of observations made by interviewers within a health care institution.
The analysis of these multilevel or nested data required that the correlation of responses by individual participants between the measurement occasions and the correlation between participant responses within schools be taken into account.
Multilevel logistic regression modelled overweight (including obese) status accounting for intraclass correlation of adolescents in households within postcode sector areas in health board regions.
To adjust for possible correlation of patients characteristics within the same medical institution and a non-linearity structure, a Box-Cox transformed, multilevel regression analysis was performed.
In a multilevel setting, correlation at a sub-level is taken care of by inclusion of random parameters which are constant within the sub-level but are allowed to vary at the upper levels [18, 20, 37].
b Regression coefficient in multilevel analysis controlling for intra correlations of household and cluster Positive regression coefficients indicate positive associations Negative regression coefficients indicate negative associations Multivariate logistic regression analysis (not shown) showed the impact of related factors on each aspect of STI knowledge of the study women.
Because the study used a multilevel sampling system, correlation among levels of sampling (classroom, school, and zone) were calculated using intraclass correlations in a random effects model.
