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Cpk/Histogram¶
Assess process capability by visualizing your data distribution against specification limits.
What is a Cpk/Histogram?¶
A Cpk/Histogram combines a histogram with process capability statistics. It shows your data distribution as bars, overlays normal curves (using within and overall standard deviation), and displays specification limit lines (USL, LSL, and optionally a Target value). Quantum XL calculates capability indices including Cp, Cpk, Pp, and Ppk, along with PPM (parts per million) defect rates.
The tool also supports distribution fitting for non-normal data (11 distribution types), data transformations (Box-Cox, Johnson), and confidence intervals for capability indices.
When to Use a Cpk/Histogram¶
- When you need to determine if a process meets its specification limits
- When you want to quantify process capability with Cpk and Ppk indices
- When you need to visualize where your data falls relative to USL and LSL
- When you want to assess the normality of your process data
- When you need to fit non-normal distributions and calculate capability from them
Example Output¶
A typical Cpk/Histogram shows bars representing the data distribution, red vertical lines at USL and LSL, overlaid normal curves, and a statistics table alongside with capability indices (Cpk, Ppk), PPM defect rates, and confidence intervals.
Learn More¶
- Examples — Step-by-step tutorials for different scenarios
- Preparing Your Data — Data types, specification limits, and subgroup options
- Options — Capability settings, chart options, distribution fitting, and more