A computer manufacturer has decided to initiate a control chart program to monitor the quality performance of their wire wrapping operation on their circuit boards. The boards are randomly tested and those that fail are sent back for rework. 40 boards are tested per day. Control limits were set at two standard deviations with target rework of 2% when the process is operation correctly. The percent of boards that required rework from 10 random samples were 3.1, 2.2, 3.0, 0.0, 2.0, 2.4, 2.1, 1.0, 1.6, 2.6.

a. What is the center line for the p chart?

b. What are the upper and lower control limits respectively for the p chart?

c. What is happening to the process?

A company is in the process of developing an acceptance plan for attributes using statistics. They have determined that the percent defectives, p-chart, should be 7% suing a sample size of 100, and with alpha equal to .05

a. What is the upper limit for the test?

b. If the number of defectives from a sample lot equals 10, what should they do about the lot?