Lean Six Sigma

Question 1

What is CTQ?

Answer 1

Critical to Quality. These represent items that are directly related to customer satisfaction.

Question 2

What are the key components to assessing defect performance?

Answer 2

DPMO = Defects per million opportunities.

Units (N) = Items produced
Defects (D) = Event that doesn't meet a CTQ spec.
Defect Opportunity (O) = CTQ's (same number)
Defective - Units with one or more defects

DPMO = 1M x (D/(NxO)

Question 3

Seven Key Principles of Lean Six Sigma

Answer 3

1 - Focus on the customer
2 - ID and understand how the work gets done
3 - Manage, improve, and smooth the process flow
4 - Remove non-value adding steps and waste
5 - Manage by fact & reduce variation
6 - Involve and equip people in the process
7 - Undertake improvement activity in a systematic way

Question 4

What is DMAIC?

Answer 4

Define - Identify key causal factors. Use interrelations map and value stream maps.

Measure - How does process look to CTQ’s?

Analyze - Check possible causes using concrete data.

Improve -

- Generate ideas about possible solutions
- Select most appropriate solution
- Plan & test solution

Control - Actions and measurement to sustain the improvements.

Question 5

What is an improvement charter and when is it used?

Answer 5

In advance of working in a Lean Six Sigma framework to solve a problem.

Contents;
High level business case
Problem statement
Goal statement
Project scope
CTQ's
Roles
Milestones

Question 6

When should reviews be undertaken during DMAIC?

Answer 6

End of Analyze - review how much you hope to achieve with project.
End of Improve phase - Did we get the results expected?
End of control phase - Were we able to sustain the results?

Question 7

Kaizan Blitz Event

Answer 7

One week sprint to solve a problem

Question 8

What is SIPOC? How do you create it?

Answer 8

Useful to focus on what needs to be measured in a system.
Suppliers
Inputs
Process
Outputs
Customers

1 - List all different customers
2 - List all outputs sent to customers
3 - Set out steps in process. Construct high level picture of the process in 4-8 steps.
4 - List all the inputs you receive from suppliers
5 - Identify where the inputs came from

Question 9

What is Kano?

Answer 9

Identifies the factors that go into customer satisfaction.

1 - Must Be’s - Obvious unspoken must have’s. If they aren’t met, significantly decrease satisfaction.
2 - One Dimensional - Features etc. The more the better (linear relationship with satisfaction).
3 - Delighters - Wow factors that surprise and delight customers.

Question 10

What are different ways to segment customers?

Answer 10

Industry
Size
Spend
Location
End Use
Product Characteristics
Buying Characteristics
Proce/cost sensitivity
Age
Gender
Socioeconomics
Frequency of purchase
Impact/opinion leader
Channel
Loyalty
Technology

Question 11

What is a customer research plan? What are methods and outputs?

Answer 11

Used to as the “Why why why!” Fully understand and develop CTQ’s.

Methods - interviews/focus groups/surveys
Output - Customer wants and needs and competitor information

For interviews - (in this order)
Learn
Clarify points
Ask for suggestions

Question 12

What should be kept in mind when developing CTQ’s?

Answer 12

Measureable
Target value and upper/lower bounds
Use paired comparison voting to prioritise

Question 13

What are the steps to mapping out a process?

Answer 13

1 - Process stapling - following a customer order throughout the process
2 - Draw spaghetti diagram of entire process
3 - Deployment flowchart, using simple icons (circle = start/stop, diamond = decision, square = step or action) with time measured in each task
4 - Value stream map

Question 14

What are the steps in creating a value stream map?

Answer 14

1 - ID the process you want to look at
2 - Set up small team for analysis
3 - Observe the work site and process in action
4 - Draw process map of material and product flow
5 - ID performance data you’d like to know
6 - Collect data needed for each step including time studies, error rates, units processed etc.
7 - Add arrows to show information flows
8 - Add overall timeline to show cycle time

Question 15

What are the steps in collecting data?

Answer 15

1 - Agree on output measures that matter for CTQ’s
2 - Agree to ground rules with team on consistently and accurately collecting data
3 - Collect data

Question 16

What are the ways and tools to identify and improve variation in a process?

Answer 16

Identify natural or special variation using control charts. If you have special variation, address this first. Work to improve natural variation through specific goals.

Question 17

How do you create a control chart?

Answer 17

Use 20 datapoints from a process, calculate the Upper Control Limit (UCL) and LCL using 3 standard deviations from the mean. Monitor the process to determine if you have special variation or natural variation.

Control charts assist in managing BY FACT and data.

Question 18

How do you determine if you have special variation in a control chart, and what do you do about it?

Answer 18

Special variation if;
1 - datapoints outside of contol limit (sometimes false alarm)
2 - If Seven consecutive points are;
- Going up
- Going down
- Above the mean
- Below the mean
- Observed cyclicality

Question 19

What is an X moving R chart and how do you construct?

Answer 19

X = datapoints
R = rolling difference between two consecutive datapoints

UCL(X) = Mean of X + (A(2)*Mean of R)
LCL(X) = Mean of X - ((A(2)*Mean of R)
*A(2) = 2.666

UCL(R) = D(4)*R
LCL(R) = D(3)*R
*D(4) = 3.267
*D(3) = 0 (LCL = 0)

Question 20

What are the different states in a control chart, what are the appropriate actions coming out of those states?

Answer 20

Ideal - Control limits within specs, data within both (Green Light!)
Threshold - Specs within control limits, data breaching specs but not control limits (Yellow Light, about to be chaos, run DMAIC)
On the Brink - Control limits within specs, data breaching control limits but not specs (Red light, about to be chaos. Run DMAIC)
Chaos = Control limits and spec limits breached by data. (Shit everywhere)

Question 21

What are the two capability indices, why are they used and how are they measured?

Answer 21

C(p) = Determines if the specs are outside of the control limits, or the process can fit within the specs.
C(p) = (USL - LSL)/(UCL - LCL)
Minimum of 1 to be “capable”

C(pk) = If process is being managed within specifications
If mean is closer to USL, C(pk) = (USL - mean (x))/ 3 stdeviations
If mean is closer to LSL, C(pk) = (mean (x) - LSL)/3 stdeviations

Question 22

What are the broad steps in the process of identifying cause and effect?

Answer 22

State problem
Brainstorm hypothesis
Create interrelationship diagram
Test and analyze to confirm or negate hypothesis

Question 23

What are statistical tools to measure cause and effect in a system?

Answer 23

X = independent variable
Y = dependent variable

State hypothesis in terms of X’s impact on Y, and chart the relationships between X’s and Y’s as strong and weak.

Measure statistical correlation between X’s and Y’s.

Question 24

What is Takt time?

Answer 24

Required cadence. The production rate required to meet demand.

eg: Takt Time = Available capacity per shift# of orders per shift
= capacity in time per unit to process

Question 25

What is OEE?

Answer 25

Overall equipment effectiveness.

A = Availability Rate = % of time equipment is up
P = Performance Rate = % of time running at designed speeds
Q = Quality rate = % of time product is built within spec

A x P x Q = OEE

Question 26

What are the 7 wastes?

Answer 26

Overproduction
Waiting
Transportation
Processing 
Inventory
Motion

Question 27

What are the “5 S’s” related to housekeeping?

Answer 27

Sort - Separate tools by frequency of use
Straighten - Put things frequenty used in easy access, remove and store others
Scrub - Keep tools and environment clean and tidy at all times
Systematize - Design operation so everything is sorted, straightened, and scrubed automatically.
Standardize - keep doing it through habit!

Question 28

What is the Red Tag Exercise?

Answer 28

Tagging items with the last used date and placing within easy reach, storing, or discarding based on the frequency of use.

Question 29

What is Jidoka?

Answer 29

Stopping an entire process when a defect occurs. This ensures the source of the defect is corrected, and no downstream defects occur as the result of one defect.

Question 30

What is FMEA?

Answer 30

Failure Mode Effect Analysis

Assign risk weights, frequency, and probabilities of detection to each risk factor, prioritize accordingly and mitigate.

Question 31

What are the 3 types of error proofing?

Answer 31

Contact - Prevent physical objects from passing through if not to spec. Ex: fixed diameter hole which product passes through to avoid larger than spec.

Fixed Value - Ensure quantities are accurate. Example, fixed size fry scoop at Mc D’s.

Motion Step - Make sure a step happens through motion detection or sensing pad.

Question 32

What are the benefits of preventative maintenance?

Answer 32

System Reliability
Decreased Replacement Cost
Decreased System Downtime
Improved Spare Inventory Efficiency

Question 33

What is Heijunka?

Answer 33

Standardized work. Avoid spikes or troughs in production.