Sample size, means and intraclass correlations of twins at 5 and 18 months separated by sex and zygosity. SchumannLyndall BoivinMichel PaquinStéphane LacourseEric BrendgenMara VitaroFrank DionneGinette E. TremblayRichard BooijLinda 2017 <p>Sample size, means and intraclass correlations of twins at 5 and 18 months separated by sex and zygosity.</p>