The variables(主语) considered（谓语） in studies（状语） are（系动词） representative of the factors（表语） believed to generate group differences, inter- and intra-individual differences（定语） that create the need for differentiated educational programming（定语）.
上面是从句子成分的角度分析.具体来讲,虽然句子很长,但其实是主系表结构.主干是：The variables are representative of the factors. 剩下的都是补充成分.相信你已经可以翻译了.