TABLE OF CONTENTS In the Analyze phase, the question to be answered is "What is wrong?" In other words, in this phase the team determines the root causes of the problems of the process. The team identified the problems of the process in the Define and Measure phases of the project.
The key deliverable from this phase is validated root causes. Anything else done in the Analyze phase is a means to get to this end. The team will use a variety of tools and statistical techniques to find these root causes. This chapter discusses some of those tools and techniques.
The team must choose the right tools to identify these root causes. The tools chosen are based on the type of data that were collected and what the team is trying to determine from the data. The team should use a combination of graphical and numerical tools. The graphical tools are important to understand the data characteristics and to ensure that the statistical analyses are meaningful (e.g., not influenced by outliers). The numerical (or statistical) analyses ensure that any differences identified in the graphs are truly significant and not just a function of natural variation.
There are a variety of graphs that can be used to better understand the data in addition to the Pareto chart presented earlier: histograms, boxplots, dotplots, scatter plots, run charts and multi-vari charts. Each graph has its own purpose.
The histogram...
