364. Cheatsheet
| Chart | Tracks | Data Typse | Sample Size | Statistical Basis | Use Case |
|---|---|---|---|---|---|
| c | Number of defects per unit | Count (discrete) | Fixed | Poisson | When you count defects per inspection unit (e.g., scratches, cracks) and sample size is constant |
| u | Number of defects per unit (standardized) | Count per unit (continuous) | Variable | Poisson | Same as c-chart but for variable sample sizes (defects per unit area, time, etc.) |
| np | Number of defective units | Count (discrete) | Fixed | Binomial | Each item is either defective or not; count how many items fail inspection |
| p | Proportion of defective units | Proportion (0-1) | Variable | Binomial | Same as np-chart but with variable sample size — tracks percentage defective |
| Mean of continuous variable | Continuous | Grouped samples | Normal | Monitors process average (e.g., length, weight, temperature) over time | |
| R | Range of values in a sample | Continuous | Grouped samples | Range distribution (based on Normal) | Used with x̄-chart to monitor variation in process (spread) |