Page 162 - Six Sigma Demystified

Chapter 6 a n a ly z e S tag e 143

recommended­Tools

The following tools (discussed in detail in Part 3) are applicable to the analyze
stage of DMAIC:

Value-­Stream­Analysis

• Flowcharts and process maps help to discover process complexities that
contribute to variation or longer cycle times.
• Program evaluation and review techniques (PERT) analysis and Gantt charts
help to identify the critical path for cycle time reduction.
• Spaghetti diagrams help to identify unnecessary movement of material or
personnel.
• Velocity is determined to prioritize cycle time improvement opportunities.

Analyzing­Sources­of­Variation

• Box- whisker chart help to graphically compare the location and variation
of various processes or categories of products or services.
• Cause- and- effect diagrams help in brainstorming potential underlying pro-
cess factors, which can be investigated in a designed experiment.
• Confidence interval on mean, confidence interval on proportion, and contin-
gency tables help to compare the means of samples from different process
conditions.
• Failure modes and effects analysis (FMEA) helps to define high- risk activi-
ties.
• Hypothesis testing of two samples and nonparametric tests on the equality of
means help to compare sample means from different conditions.
• Statistical process control (SPC) charts, including C, Np, P, U, Individual- X,
X- bar, and EWMA charts, help to differentiate between special and com-
mon causes of variation.
• Multi-vari plots help to categorize variation and investigate interactions
among factors.
• Pareto charts help to focus on areas with greatest opportunity.
• Histograms help to graphically display the process output relative to
requirements.