Question

The accompanying observations are numbers of defects in 25 1-square-yard specimens of woven fabric of a certain type: 4, 7, 5, 2, 3, 1, 9, 3, 4, 3, 5, 7, 3, 2, 2, 4, 7, 3, 2, 5, 5, 1, 4, 4, 5. Construct a c chart for the number of defects. (Round your answers to two decimal places.)

x double bar =
LCL =
UCL =

Answer 1

x double bar = 4

LCL = - 2

UCL = 10

Explanation:

The C - chart :

The control limit = xbar

xbar = mean = ΣX / n

The upper and lower control limit :

Xbar ± 3√xbar

Xbar = Σx / n = 100 / 25 = 4

Hence,

x double bar = 4

LCL = Xbar - 3√xbar = 4 - 3√4 = 4 - (3*2)

LCL = 4 - 6 = -2

UCL = Xbar + 3√xbar = 4 + 3√4 = 4 + (3*2)

LCL = 4 + 6 = 10