In the Analyze phase of the Six Sigma DMAIC methodology, root cause analysis techniques like 5 Whys, fishbone diagrams, and data analysis including hypothesis testing and ANOVA are used. The 5 Whys technique is used to identify root causes by repeatedly asking "Why?" until the fundamental reason is found. A problem that cannot be reproduced has not truly been resolved, so it is important to challenge identified root causes by attempting to reproduce any defects.