Data organisation and preparation for statistical analysis in a longitudinal birth cohort.

Prior to the commencement of a birth cohort study it is important to take account of the different ways in which statisticians will want to use the data. Here we suggest issues to be considered and possible solutions. We include details of data preparation from questionnaires or interviews; biological and genetic assay results; preparation of clean edited files; types of statistical analyses that are appropriate, and issues surrounding whether the data should be put into the public domain.