Question

construction company has just constructed 150 new apartments. An external inspector is hired to do the final checking before they are given way to prospective customers. Inspector at random selects 8 apartments and and counts how many defects are in each one them. He finds 7,3, 2, 1, 2, 5, 4, 4 defects. What will be Upper Control Limit for a C chart

Answer 1

Upper Control Limit for a c-chart = 9.1

Explanation:

Given - construction company has just constructed 150 new apartments. An external inspector is hired to do the final checking before they are given way to prospective customers. Inspector at random selects 8 apartments and and counts how many defects are in each one them. He finds 7,3, 2, 1, 2, 5, 4, 4 defects.

To find - What will be Upper Control Limit for a C chart ?

Proof -

Upper Control Limit for a c-chart = c bar + 3(square root of c bar)

Now,

c bar =
`(7+3+2+1+2+5+4+4)/(8)` = 3.5

∴ we get

Upper Control Limit for a c-chart = 3.5 + 3(square root of 3.5)

= 3.5 + (1.87)

= 3.5 + 5.61

= 9.1

⇒Upper Control Limit for a c-chart = 9.1