the science concerned with "the collection, organization, analysis, interpretation, and presentation of data."

Principles of Statistical Thinking

• All work occurs in a system of interconnected processes
• Variation exists in all processes
• Understanding and reducing variation are the keys to success

Variation

• Many sources of uncontrollable variation exist (common causes)
• Special (assignable) causes of variation can be recognized and controlled
• Failure to understand these differences can increase variation in a system

Sources of Variation in Production Processes

• Inputs- Materials and Tools
• Processes- Operators, Methods, Machines, Environment
• Outputs- Measurement instruments, Human inspection performance

• Variation increases unpredictability
• Variation reduces capacity utilization
• Variation contributes to a "bullwhip" effect
• Variation makes it difficult to find root causes
• Variation makes it difficult to detect potential problems early

1. Treating as a special cause any fault, complaint, mistake, breakdown, accident or shortage when it actually is due to common causes
2. Attributing to common causes any fault, complaint, mistake, breakdown, accident, or shortage when it actually is due to a special cause