## Find and analyze possible causes

Collect and analyze information to determine possible causes in order to select the real cause of the problem.

**Most used tools:**-Ishikawa diagram (including NGT).

-Stratification

-Scatter plot

-Check sheets

## Ishikawa diagram

**Definition:**Diagram that shows the possible sorted causes of a problem.

**Process elements:**

- - Methods
- - Men
- - Raw materials
- - Measurement
- - Environment
- - Machinery and equipments

*Steps: Based on a process of “brainstorming”:*

1.- Each member generates a single idea (cause) each round. All of the ideas are numbered and registered.

2.- Discard repeated ideas.

3.- Verify that the remaining ideas are related to the problem (discuss).

4.- Place the resulting ideas into the appropriate

category in the Ishikawa (cause-and-effect) diagram.

*Example 1) Hypothetical example involving scrap in a certain area:*

## Stratification

**Definition:**Technique used to analyze information based on the classification of its origins.-
*Some examples of strata are machinery by model or type, workers (training, shift,gender), raw material (supplier, lot), and the operating conditions (temperature,humidity...).*

**Example 1) Suppose a certain factory produces the same product in three different areas. Each area has three identical machines. The following table shows information on the number of defects in the three areas:**

After analyzing the data a new table is obtained based on the information by area.

They now decide to stratify the above information for area 3:

## Scatter plot

**Definition:**A simple graph of two variables. You can visualize the type and the degree of relationshiop (correlation) between these two variables.

### Type of relationship

### Degree of relationship

**How to do it?**We will use the Microsoft Excel to help in the process.

**Example 1) The table below shows information about the hardness of a group of manifolds vs. their solidification time. Draw and interpret a scatter plot. **

## Check sheets

**Definition:**Forms to collect, analyze and report information. Standardize and facilitate the collection, analysis and reporting of information.

**Types**

1.- To visualize distributions

2.- To score the total number of defects by type

3.- To locate defects

4.- To stratify the number of defective units

5.- Check list

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