IASSC Certified Lean Six Sigma Black Belt (ICBB) — Question 36

________________________ chart is used to count data (defects) with variable sub groups.

Answer options

• A. np chart
• B. u chart
• C. X-bar and S chart
• D. c chart

Correct answer: C

Explanation

The X-bar and S chart is appropriate for monitoring the mean and variability of a process when data is collected in variable subgroups. The np chart is used for attribute data where the sample size is fixed, the u chart is for variable subgroup data with non-constant sample sizes, and the c chart is for counting the number of defects in a constant sample size, making them unsuitable for this scenario.