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Data integration, i.e. the use of different sources of information for data analysis, is becoming one of the most important topics in modern statistics. Especially in, but not limited to, biomedical applications, a relevant issue is the combination of low-dimensional (e.g. clinical data) and high-dimensional (e.g. molecular data such as gene expressions) data sources in a prediction model. Not only the different characteristics of the data, but also the complex correlation structure within and between the two data sources, pose challenging issues. In this paper, we investigate these issues via simulations, providing some useful insight into strategies to combine low- and high-dimensional data in a regression prediction model. In particular, we focus on the effect of the correlation structure on the results, while accounting for the influence of our specific choices in the design of the simulation study. [ABSTRACT FROM AUTHOR]

Objective Verbal fluency (VF) tasks are widely used to investigate children's lexical knowledge and executive functions skills. Consistency of measurement of the strategic retrieval components is still an issue and performance of Brazilian–Portuguese speaking children are currently not available. A cross-sectional study investigated the effects of age, school type (public × private) and the influence of language, memory and inhibitory control on VF. Method We assessed 414 Brazilian children, aged 6–12, in the number of words produced and both clustering and switching components, with two measures of VF: letter (LVF) and semantic (SVF). Results Analysis of the number of words produced showed a significant increase between 6–8-year-olds, 9–10-year-olds and 11–12-year-olds in SVF, while in LVF, the differences were significant only in the later age group. In SVF, the numbers of clusters and switches increased with age, whereas in LVF, the number of switches increased in all age groups, but clusters increased only in the older group. Structural equation model analyses showed that oral and written language, verbal memory and inhibitory control are associated with VF performance and IQ, while age mediated VF performance. Conclusions The results indicate a different development pattern between LVF and SVF in the number of words produced and in clustering and switching, with the latter predicting VF performance in words produced. VF development is shown to depend on language, memory and inhibitory control. Our results have important implications to clinical neuropsychology. [ABSTRACT FROM AUTHOR]