Question

1. Why are (1) statistical inference, (2) predictive statistics, (3) prescriptive statistics, and (4) descriptive statistics methods important to Six Sigma?

Describe the structure of a cause-and-effect diagram.

What is a root cause? How does the “5 Why” technique help uncover the root cause?

Answer 1

Cause and effect diagram

This technique investigate why something happened or might happen by identifying possible causes in smaller categories.It can also be very usefull to find the relationship between contributing factors for effect.

To start making a cause and effect diagram, first write the main issue to be analyzed in a box that is typically on the right edge of the page, halfway down the page. A line called the "backbone" should extend to the left starting from the edge of the main box. Next, angle branches off of the backbone, each representing a cause or effect of the main issue. Each of these branches can contain additional branches.

Common practice used in Industry are;

1)Identify the issue

2)Do brainstroming session to categorise all possible causes.

3)Draw the backbone diagram

4)Add all the possible causes and effects into the diagram

5)Analyze the complete diagram by given all information

Root cause; This is the possible starting point in chain of cause and effect reactions. In simple term, this is the basic reason for major problem in terms of quality in any industry.

5 Why; This is used in analyze phase in DMAIC methodology in six sigma.

By asking the question “Why” (five is a good rule of thumb), you can peel away the layers of symptoms which can lead to the root cause of a problem. Very often the possible reason for a problem will lead you to another question.In answering so, will come up with another question and doing so we come up at root cause of the problem.This is not like you only have to ask 5 questions, you may ask higher or lesser than 5 question, but only aim is to come at the main instigating factor which leads to major concern from quality perspective.

Advantage of 5 why is;

*Identify the root cause

*Find the relationship between different causes

*Does not require any statistical analysis

Steps to complete 5 why;

a)Write down all specific concerns. Writing the issue helps you formalize the problem and describe it completely.

b)Ask among the group of teammates, Why the problem happens and write the answer down below the problem.

c)If the answer you just provided for all the questions doesn’t identify the root cause of the problem that you wrote down in Step a, ask Why again and write that answer down.

*Loop back to step c until the team is in agreement that the problem’s root cause is identified. Again, this may take fewer or more times than 5 Why