Quality Tools and Charts - Pareto and Histogram

Basic Quality Tools

• Histograms are graphs that show the frequency of numerical data using rectangles.
• The height of a rectangle (the vertical axis) represents the distribution frequency of a variable.
• Use histograms when:
  • Data are numerical
  • Want to see the shape of the data's distribution
  • Analyzing whether a process can meet customer's requirements
  • Analyzing a supplier's process output
  • Seeing if a process change has occurred over time
  • Determining if outputs of two or more processes are different
  • Communicating data distribution quickly and easily to others

Scatter Diagrams

• Scatter diagrams are two-dimensional graphical representations of a set of data.
• They graph pairs of numerical data with one variable on each axis to look for a relationship between them.
• Correlation patterns:
  • Strong Positive: Y increases as X increases
  • Strong Negative: Y decreases as X increases
  • Weak Positive: Y increases slightly as X increases
  • Weak Negative: Y decreases slightly as X increases
  • Complex: Y is related to X, but the relationship is not easily determined
  • No Correlation: No demonstrated connection between the two variables

Control Charts

• Control charts are used to determine if a process is in a state of statistical control or how much variation exists in a process.
• They are graphs used to study how a process changes over time.
• Also known as Shewhart Charts or Statistical Process Control Charts (SPCC)

Root Cause Analysis

• Root cause analysis is the process of discovering the root causes of problems to identify appropriate solutions.
• The root cause is the core issue that sets in motion the entire cause-and-effect reaction that ultimately leads to the problem(s).

Pareto Charts

• Pareto charts are powerful tools for showing the relative importance of problems.
• They contain both bars and lines, where individual values are represented in descending order by bars, and the cumulative total of the sample is represented by the curved line.
• Use Pareto charts when:
  • Analyzing data about the frequency of problems or causes in a process
  • Focusing on the most significant problems or causes
  • Analyzing broad causes by looking at their specific components
  • Communicating with others about data
• The 80/20 Rule (Pareto principle or law of the vital few & trivial many) states that roughly 80% of the effects come from 20% of the causes.

This quiz covers the basics of quality tools, focusing on Pareto charts and histograms, used in quality control and management.