Question

A shirt manufacturer buys cloth by the 100-yard roll from a supplier. For setting up a control chart to manage the irregularities (e.g., loose threads and tears), the following data were collected from a sample provided by the supplier.

SAMPLE	1	2	3	4	5	6	7	8	9	10
IRREGULARITIES	3	5	2	6	5	4	6	3	4	5

a. Determine the c¯, UCL and LCL for a c-chart. (Round your answers to 2 decimal places.)

c-bar =

UCL =

LCL=

Answer 1

Ans a)

is the average value of the number of irregularities in the samples

= (3 + 5 + 2 + 6 + 5 + 4 + 6 + 3 + 4 + 5) / 10

= 4.30 irregularities

We will use a Z-value of 3 which signifies a 3 sigma control limit.

Upper control limit (UCL_c) is-

UCL_c = 10.52 irregularities

Lower control limit (LCL_c) is-

LCL_c = -1.92 irregularities

The Lower control limit for the C-chart is 0 as negative irregularities have no meaning.