Software product lines have a demonstrated potential for cost-effective development of software families. Product lines have to support and coordinate variabilities between the different members of the product family. However, it is also known that the management of these variabilities and the concurrent evolution of product line architecture and single products are still challenging tasks [1]. This organizational overhead often prevents small and medium enterprizes with limited software development staff from adopting product lines. This paper introduces three classes of product line variability and discusses their impacts to product line architectures. In particular, we discuss the management of these variabilities, by introducing a pattern-based product line architecture and an associated pattern language for statistical analysis software.