Process Capability & Statistics
40 practice questions with explanations — 15 free to try
PassNova has 40 Lean Six Sigma Green Belt practice questions on Process Capability & Statistics, each with a clear explanation. A 15-question taster is free with no sign-up; the full bank is part of PassNova Premium. Updated for 2026.
Process Capability & Statistics: example questions & answers
3 worked examples with answers and explanations below. Try 15 Lean Six Sigma Green Belt questions free in the browser; the full 40-question Process Capability & Statistics bank is part of PassNova Premium.
A process has USL = 110 and LSL = 90, with a standard deviation of 2.5. What is the process potential capability Cp?
- A2.00
- B0.75
- C1.00
- D1.33✓
Answer: Cp = (USL - LSL) / (6 x sigma) = (110 - 90) / (6 x 2.5) = 20 / 15 = 1.33.
For the same process (USL = 110, LSL = 90, sigma = 2.5) with a mean of 104, what is Cpk?
- A0.80✓
- B1.07
- C1.33
- D1.87
Answer: Cpk = min[(USL - mean), (mean - LSL)] / (3 x sigma) = min[(110-104), (104-90)] / 7.5 = min[6, 14] / 7.5 = 0.80.
Under what condition does Cpk equal Cp for a process?
- AWhen the process is out of statistical control but still within specification
- BWhen the process variation is very large compared with the specification width
- CWhen the process mean is exactly centred between the specification limits✓
- DWhen the sample size is below 30 and the normality assumption cannot be checked
Answer: Cpk equals Cp only when the process is perfectly centred between the specification limits; any off-centring makes Cpk less than Cp.