This paper assesses how well quality tools identify the correct root cause with a modified usage compared to more traditional usage. The purpose of this research is to empirically evaluate the use of a modified Ishikawa diagram and variation of another quality tool for identifying testable hypotheses in root cause analysis. Two experiments were performed using engineers to evaluate the proposed methods for hypothesis selection and evaluation. One study evaluated the use of an Ishikawa diagram with a hypothesis related action item tracking list versus teams with just an Ishikawa diagram. The second study determined if the correct hypothesis was selected more often than chance when multiple hypotheses and observations are presented in a list. Use of the proposed method including a modified Ishikawa diagram leads to more testable hypotheses and listing the available evidence can lead to the identification of the correct hypothesis.