Data Analysis Techniques: Stratification and Cause-Effect Diagrams

Methodology Steps for Analysis

The following steps outline a process for analyzing data, likely related to quality or process issues:

1. Establish a list of reasons.
2. Appreciate the importance of each cause.
3. Calculate the percentage ratings.
4. Classify as growing percentages obtained.
5. Rendering a column chart.
6. Plotting the graph of the cumulative values (Dickey curve).
7. Determine areas A, B, and C.

5. Estratificación (Stratification)

What is it? Why?

Stratifying the data collected involves subdividing it into a number of homogeneous groups to facilitate understanding and analysis of the phenomenon under study. The goal is to define the factor or factors most significant in terms of data representing the phenomenon.

Stratification should be used in the approach to data collection and can be applied using various tools such as data collection sheets, histograms, and Pareto diagrams. The data are classified according to logical homogeneous subdivisions (or stratification factors).

Methodology for Stratification

1. Defining the characteristic or phenomenon to be analyzed.
2. Representing data in a general way.
3. Identifying the most suitable stratification factors.
4. Classifying the available data into homogeneous groups according to the selected stratification factors.
5. Graphed each homogeneous group of data.
6. Comparing the homogeneous groups of data within each factor to see if differences are detected.

3. Diagrama Causa-Efecto (Fishbone or Ishikawa)

What is it? Why?

The cause-effect diagram is a graphical representation technique that:

• Allows you to identify possible causes associated with a problem (effect).
• Structures the possible causes using a series of generic factors.

It is useful to identify and sort the causes and origins to solve the problem from its root. The effect may be a particular problem you want solved or a goal that you want to achieve.

Methodology for Cause-Effect Diagram

1. Define clearly the effect.
2. Identify the factors influencing the activity associated with the effect.
3. Determine subcauses for each cause and associate them.
4. Build the chart and check the logic of the causal chain.
5. Take data on the causes of the problem to determine the degree of influence of each and to refine the conclusions and define solutions.

4. Diagrama de Pareto (Pareto Chart)

What is it? Why?

The Pareto chart is a graphical representation technique that classifies the causes of a problem according to their importance, based on their frequency or cost. It is a histogram in which the variable values or ranges are listed in descending frequency.

It is useful to identify the most influential factors in a particular situation and determine the relative importance of different causes. The Pareto Principle states that 20% of the reasons cause 80% of the defects observed.