3- The Analysis Tollgates

The third step in applying Six Sigma DMAIC is Analysis. During this step, the team analyzes data and the process itself, finally leading to determining the root causes of the poor sigma performance of the process.

There are three Analysis tollgates: Data Analysis, Process Analysis, and Root Cause Analysis.

1. Data Analysis

The type of data analysis is dependent on the type of data collected in the measure phase of DMAIC, discrete or continuous.

1-DISCRETE DATA ANALYSIS:

When data collected in the measure phase of DMAIC is discrete in nature, the most common statistical tools we use are the Pareto chart and the Histogram.

2-CONTINUOUS DATA ANALYSIS

Continuous data that is collected in the Measure phase of the DMAIC project is collected using the frequency distribution check sheet.

3- THE RUN CHART

Another continuous data analysis tool is the run chart. A run chart tracks some value over time allowing us to see if there are any shifts or trends in the data.

The horizontal line indicates the average wait for the drive-thru line is 3.95 or four minutes. However, by tracking the data over time using a run chart, we can see an increasing trend in the data.

2. Process Analysis

Process analysis includes creating a more detailed process map and analyzing the more detailed map for where the greatest inefficiencies exist.

PROCESS ANALYSIS: SUBPROCESS MAPPING

For purposes of process analysis, subprocess mapping refers to taking one or more high-level process step from the original high level map and “drilling down” to the five to seven steps below the high level. Often these steps will reveal inefficient, non-value-added steps that later the team should attempt to change or even remove.

PROCESS ANALYSIS: THE NATURE OF WORK

Once the subprocess map has been created and validated by the project team, they need to analyze the map for where non-value added steps are located.If any step does not meet all three criteria, the step is considered non-value-added. Each nonvalue-added step then must be categorized into one of the following types of non-value-added activities:

• Internal failure: Steps that must be done more than the first time.

• External failure: Failures in the process detected by the customer.

• Delays: Waits in the process.

• Control/inspection: Steps in the process that verify previous work has been done correctly.

• Preparation/set-up: Steps in the process that prepare a following step to be done.

• Moves: Steps that move a product or element in service from one place to another.

• Value enabling: A non-value-added step in the process that would not be targeted for improvement because it is necessary for the functioning of the organization.

MICRO PROBLEM STATEMENTS: THE LAST STEP IN DATA AND PROCESS ANALYSIS

The microproblem statement is actually phrased in the form of a question that begins with the word,“Why ” Microproblem statements allow the project team to become more specific with regard to the problem they are trying to impact. Microproblem statements come from either data analysis or process analysis.

3. Root Cause Analysis

The third and most important tollgate of Analysis is root cause analysis.

THE THREE STEPS TO ROOT CAUSE ANALYSIS

Project teams must go through three important steps for root cause analysis to be done properly. They are:

1. The open step: During this phase of root cause analysis, the project team brainstorms all the possible explanations for current sigma performance.

A simple formula to help the team through root causation is:

Y = f(x)

The Y in this formula refers to the problem associated with the microproblem statement.(the xs) process variables that could explain the problem stated in the microproblem statement

2. The narrow step: During this phase, the project team narrows the list of possible explanations for current sigma performance.

3. The close step: During this phase, the project team validates the narrowed list of explanations that explain sigma performance. Testing the narrowed list of potential root causes can be done through Scatter analysis.

4-The Improve Tollgate

There are two Improve tollgates, generating solutions and selecting solutions.

It is recommended that when implementing solutions, the project team prioritizes the solutions and implements them one at a time or in groups, immediately following implementation of the solutions with a recalculation of sigma. This should be done because many times the goals and objectives of the project team may be achieved without implementing all the proposed solutions.