DMAIC: Define, Measure, Analyze, Improve, Control

1. Define

(1) Develop problem and goal statements

Problem Statement

• Requirements: Reccuring, Specific, and Measurable
• Example: the problem stated below is a chronic, reccuring problem, stated in specific and measurable terms

Goal Statement

• Ask ourselves: What measurable perforance outcome must the project accomplish? By when?
• Be SMART:
• Example:

We need to define what is the $Y$, the performance measure to improve, in the equation of $Y=f(x)$

(2) Develop project charter

A document providing direction and focus to the team:

• Project name
• Problem and goal statements (based on step one above)
• Key Metric $Y=f(x)$
• Expected benefits (operational and finantial)
• Project scope (project boundary)
• Milestones (check point datas)
• Signatures
  • Project leader: agrees to take on project
  • Finance: validates expected financial benefits
  • Champion: approves launch of the project

(3) Develop a SIPOC diagram

Purpose is to document and communicate overall scope of processes related to the project on one page

2. Measure

Steps:

1. Develop data collection plan
2. Map relevant processes
3. Validate measurement system
4. Measure the $Y$ in $Y=f(X)$

(1) Data collection plan:

1. List specific questions regarding $Y$
2. Tools needed
3. Sources of data
4. Type (continuous/discrete) and quantity of data required

Continuous data graphs:

Discrete data graphs:

(2) Process Map:

A visual representation of the steps that take place in a process, from start to finish. Ex: Wake-up-and-get-to-work Process

(3) Validate Data: use Measurement system analysis (MSA)

Requirements of a valid measurement: (using an example of weight scale 体重秤)

• Accurate with no bias: the scale should be calibrated
• Repeatable: if I weigh myself twice in a short time, the results should be same
• Reproducible: my weight in my home should be the same as my weight in my doctor’s office

3. Analyze

Purpose: Determine which $X$(s) impact $Y$ in $Y=f(X)$

Steps:

1. List potential $X$(s) that impact $Y$
2. Organize potential $X$(s)
3. Shortlist and select key $X$(s)
4. Develop data collection plan for the analysis
5. Prove the key $X$(s) in $Y=f(X)$

(1) List potential $X$(s) that impact $Y$: brainstorm

(2) Organize potential $X$(s): use Cause-effect diagram (fishbone)

Ex: CE Diagram for Pizza Crust Problem (饼皮太硬)

• Fishbone:
• Treemap (use Excel):

(3) Shortlist and select key $X$(s): based on the upper diagram

(4) Develop data collection plan for the analysis

• Which hypotheses to test
• What data to collect
• How much data we need
• Collect from whom, when, where

(5) Prove the key $X$(s) in $Y=f(X)$: Validation Process

• Inferential statistics
• Hypothesis test

Ex: Analyze and validate throught graphs and charts, using Pizza Crust Problem (饼皮太硬问题). To validate two potential $X$

• $X_1$: one or two resteraunt at fault
• $X_2$: Variation in oven temperatures

$X_1$ is proved using Pareto Chart for Crust Complaints by Store Location

$X_2$ is proved using Dotplot and Boxplot for Temp Variation by Chef

4. Improve

Purpose: Address proven key $X$(s) and find solutions (best combination of key $X$(s)) to improve $Y$

Steps:

1. Potential solutions for proven key $X$(s)
2. Solution alternatives
3. Right set of solutions to implement

Generate, evaluate, and select solutions

Evaluate solutions:

Select solutions: Pugh Matrix (Criteria selection matrix)

Reduce the risk of failure through FMEA

FMEA (Failure Modes and Effect Analysis) is a tool to help anticipate and mitigate risk of failure.

Order failure modes by Risk Priority Number (RPN):

• $\text{Severity}$: What’s the effect? How severe is it (1-10)?
• $\text{Occurrence}$: What are potential causes? How likely is the occurrence of potential causes (1-10)?
• $\text{Detection}$: What process controls are in place to detect cause or failure mode? What’s the likelihood of detection (1-10)?

Mistake proofing (防范错误)

Adding mistake proofing to projects will be helpful. Three levels of mistake proofing:

1. Prevention
   • Ex: Change the operation sequence of ATM to prevent forgeting to remove card after taking cash
   • Swap steps 4 and 6, that is, can only take cash after removing card
2. Facilitation: if prevention is not applicable
   • Ex: To avoid the cashier typing an inccorect price, try to scan Bar Code instead
3. Detection:
   • Ex: Spelling error detection in Word

5. Control phase:

Purpose: Control of key $X$ factors to ensure improved $Y$ is sustainable

Steps:

1. Develop plan (Monitor, control, regulate performance)
2. Work with owners to update procedures
3. Implement and monitor performance
4. Validate financial impact
5. Secure project completion sign-off

Control Plan

Control plan is the blueprint to ensure the right controls are implemented to achieve sustainable targets:

1. Control subject: what needs to be controlled
   • Ex: oven temperature
2. Specification, target, or desired range
   • Ex: target 22C, hot more than 24C, cold less than 19C
3. How feedback is provided
4. When and what action to take
   • Ex: when temp above 25, turn off AC; when below 15, turn off AC, or turn on heat if needed
5. Who is authorized to monitor and take action?