The SPC Decision Tree
Selecting the wrong control chart is the most common error in statistical process control. Use this interactive wizard to ensure mathematical compliance with ISO 7870 standards.
Foundational Category: Statistical Process Control (SPC) • ~4 min read
Control Chart Decision Wizard
Eliminate chart misapplication by mapping data type, subgroup size, defect nature, and sensitivity needs.
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Q:
How do I choose the correct Control Chart for my data?
First determine your data type: Variables (Continuous) or Attributes (Discrete). For variables, select by subgroup size: n=1 (I-MR), n=2..8 (X-bar & R), n>8 (X-bar & S). For attributes, select by count type: defectives (p or np chart) vs defects per unit (c or u chart).
Step 1: Data Measurement Type
Step 2: Subgroup & Sampling Context
Recommended Control Chart
X-bar and R Chart
The standard industrial SPC chart for continuous data with rational subgroups n = 2 to 8.
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Recommended Next Steps in Quality Workflow
Statistical Process Control (SPC)
X-bar and R Control Chart
Detect assignable causes of variation and establish statistical control limits.
Statistical Process Control (SPC)p Chart for Fraction Defective
Track defect rates across varying production lot sizes while accounting for overdispersion.
Statistical Process Control (SPC)Individuals and Moving Range (I-MR) Chart
Establish control limits for low-volume production, destructive tests, and batch chemical processes.