Zurn Pex, Inc. (Zurn) (defendant) is in the business of designing plumbing systems. Zurn’s plumbing systems were designed to use materials containing a certain type of brass fittings, which made the plumbing systems prone to corrosion and premature failure. Denise and Terry Cox (plaintiffs) allege that their home was damaged due to leakage caused by the Zurn pex plumbing system installed in their home. They brought this suit claiming violations of Minnesota consumer protection statutes, negligence, and breach of warranty. A number of related lawsuits involving Zurn pex plumbing systems were subsequently filed. All such cases were transferred to this court, and the various plaintiffs sought to be certified as a class. In support of the plaintiffs’ motion for class certification, the plaintiffs offered expert testimony from Dr. Blischke, who analyzed warranty claims data, and Dr. Staehle, who performed tests on the brass fittings. The defendants challenged the expert testimony.