Number Generator
Generate random numbers, data with a chosen mean and sigma, or data that hits a target Cpk
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Generates random numbers in a range, normal data with a chosen mean and sigma, or data that hits a target Cpk. Use it to make example data for teaching process capability or for testing forms and software.
How to use
- Under "Method", choose "Random numbers", "Mean and sigma" or "Target Cpk".
- Under "Data layout", set "How many" for "Individual values", or the size and number of subgroups for "Subgroups (n × k)".
- Enter the range, the mean and sigma, or the spec limits and "Target Cpk"; the values, statistics and a histogram appear at once.
- Use "Copy values (pastes into Excel)" or "Save as CSV", or a button such as "Send to Process Capability Calculator".
How it works
- Up to 10,000 values can be generated at once. Subgroup size is 2 to 25, and decimal places are 0 to 6.
- "Match exactly" rescales the values so the sample mean, sigma and Cpk equal the targets. If rounding makes that impossible, the closest values are used and the tool says so.
- Within sigma is estimated as R-bar/d2 for subgroups and MR-bar/1.128 for individual values.
- The numbers are generated, not measured. Using them in real quality records such as inspection reports is data falsification.
Questions and answers
- How do I generate data with a Cpk of 1.33?
- Choose "Target Cpk" and enter an LSL of 9.5, a USL of 10.5 and a target of 1.33. With no shift, the tool uses a mean of 10 and a sigma of 1 ÷ (6 × 1.33) ≈ 0.1253.
- What is the difference between Cpk and Ppk?
- Cpk uses the sigma estimated from within-subgroup variation; Ppk uses the standard deviation of all the data. The table shows both, and "Sigma to match" sets which one meets the target.
- Can I get the same random numbers again?
- Yes. The same "Seed" with the same settings gives the same result. Press "Generate again with a new seed" for different data.
- Can I draw random numbers without repeats?
- In "Random numbers", keep "Integers" and turn on "No repeats", for example to draw 6 numbers from 1 to 45. Asking for more numbers than the range holds shows a message.