ASQ Certified Six Sigma Black Belt (CSSBB) — Question 3

Using this partial Z Table, how many units from a months production run are expected to not satisfy customer requirements for the following process?
Upper specification limit: 7.2 Lower specification limit: 4.3 Mean of the process: 5.9 Standard Deviation: 0.65 Monthly production: 450 units

Answer options

• A. 3
• B. 7
• C. 10
• D. 12

Correct answer: C

Explanation

The correct answer is C because the calculated Z-scores for the upper and lower specification limits indicate the proportion of units outside the acceptable range. By applying this proportion to the monthly production of 450 units, we find that approximately 10 units are expected to fail to meet customer requirements. Options A, B, and D are incorrect as they underestimate or overestimate the number of non-compliant units.