S6.14 You are attempting to develop a quality monitoring sys tem for some parts

ID: 354039 • Letter: S

Question

S6.14 You are attempting to develop a quality monitoring sys tem for some parts purchased from Charles Sox Manufacturing Co. hese parts are either good or defective. You have decided to take a sample of 100 units. Develop a table of the appropriate upper and lower control chart limits for various values of the average fraction defective in the samples taken. The values for p in this table should range from 0.02 to 0.10 in increments of 0.02. Develop the upper and lower control limits for a 99.73% confidence level. N= 100 UCL LCL 0.02 0.04 0.06 0.08 0.10 Px

Explanation / Answer

It is given that the sample size = n = 100

Following formula to be noted for Upper Control Limit and Lower Control Limit for p bar :

UCLp = Pbar + 3 x Square root ( pbar x ( 1 – pbar)/n )

LCLp = Maximum ( 0 , ( Pbar – 3 x Square root ( pbar x ( 1 – pbar)/n) )

Accordingly relevant values of UCL and LCL for different values of pbar are as follows :

Pbar

UCL

LCL

0.02

0.062

0.04

0.0988

0.06

0.1311

0.08

0.1613

0.10

0.19

0.01