Chapter 2: Basic Statistical Concepts for Statistical Process Control
Abstract: Basic Statistical Process Control (SPC) concepts involve monitoring processes with control charts to distinguish between common cause (random) and special cause (assignable) variation , using central tendency (mean, median) and dispersion (standard deviation) to set Upper/Lower Control Limits (UCL/LCL) , aiming for stability and continuous improvement by detecting when a process drifts from expected patterns. Key Concepts Variation: All processes have variation, which SPC aims to understand and reduce. Common Cause Variation : Inherent, random variation due to chance; a stable process is only affected by common causes. Special Cause Variation : Non-random, identifiable causes (e.g., machine malfunction, human error) that make a process unstable and require action. Central Tendency : Measures the center of the data. Mean: The average. Median: The middle value. Dispersion : Measures how spread out the data is, often using Standard Deviation ...