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Topics: Quality, Using PMI Standards
Different answers to Same question about the quality management tools application.
Dear Senior,

I am very confusing the application of two Quality Management Tools, which are CAUSE & EFFECT DIAGRAMS and SCATTER DIAGRAMS. Because two top10 PMP training institutes, which authorized by PMI, in China give different answer to the same question as below:
Due to quality control issues, a project is behind schedule. There is no obvious pattern to the
identified defects. Using a qualitative approach, which quality control tool should be used to
determine the source of the defects?
A. Histogram
B. Pareto chart
C. Scatter diagram
D. Cause and effect diagram

One of this two training institutes say: C is right answer. Another say: D is right answer.

I will very appreciate any senior PMP tell me which is right answer. The will be PMP examination on 10th of Sep.

Yichi Xing.
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Scatter diagraim is used to find a pattern if exits. I think D is the right answer
Let's understand what's Scatter Diagram & Cause and Effect Diagram first.

As per ASQ :

Scatter Diagram

Also called: scatter plot, X–Y graph

The scatter diagram graphs pairs of numerical data, with one variable on each axis, to look for a relationship between them. If the variables are correlated, the points will fall along a line or curve. The better the correlation, the tighter the points will hug the line.

When to Use a Scatter Diagram

- When you have paired numerical data.
- When your dependent variable may have multiple values for each value of your independent variable.
- When trying to determine whether the two variables are related, such as…
- When trying to identify potential root causes of problems.
- After brainstorming causes and effects using a fishbone diagram, to determine objectively whether a particular cause and effect are related.
- When determining whether two effects that appear to be related both occur with the same cause.
- When testing for autocorrelation before constructing a control chart.

Fishbone (Ishikawa) Diagram

Also Called: Cause–and–Effect Diagram, Ishikawa Diagram

Variations: cause enumeration diagram, process fishbone, time–delay fishbone, CEDAC (cause–and–effect diagram with the addition of cards), desired–result fishbone, reverse fishbone diagram

The fishbone diagram identifies many possible causes for an effect or problem. It can be used to structure a brainstorming session. It immediately sorts ideas into useful categories.

When to Use a Fishbone Diagram
- When identifying possible causes for a problem.
- Especially when a team’s thinking tends to fall into ruts

Now let's read the question again. Look at the words - "there is no obvious pattern to the identified defects" , "using a qualitative approach"

The most obvious choice in this case is 'D'.
I would defintely vote for "D"
Given the context of the question, my vote goes in favour of D
Many thanks all input from all seniors of PMI family. Yes, my original is also to select D. All input remedy my thinking and understanding about the PMP knowledge, and give me clean guideline to keep me always on right way.

Thanks again to all input like a family.

Yichi Xing
The answer is inside the PMBOK itself. Check Project Quality chapter. And do not pay attention to the first part of the question.

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