A subassembly is inspected and the number of defects recorded. A new group of assemblers began work Monday morning. The number of defects per subassembly for the first 10 they produced was: 3,2,0,5,4,6,0,7,7,and 6. What are the upper and lower limits for the c-bar chart?
A)15 and 0
B)10 and 0
C)1.12 and 0
D)6 and −2

Question

Quizplus · Accepted Answer

The c-bar chart is used to monitor the number of defects per subassembly. The upper control limit (UCL) and lower control limit (LCL) for c-bar chart can be calculated using the following formula:

UCL = c̅ + 3√c̅
LCL = c̅ - 3√c̅

where c̅ is the average number of defects per subassembly.

Using the given data, we can calculate c̅ as:
c̅ = (3+2+0+5+4+6+0+7+7+6)/10
c̅ = 4

Substituting this value of c̅ in the above formula, we get:
UCL = 4 + 3√4
UCL = 10
LCL = 4 - 3√4
LCL = 0

Therefore, the upper and lower limits for the c-bar chart are 10 and 0, respectively. Hence, the answer is B.

A Subassembly Is Inspected and the Number of Defects Recorded