Engineers want to set up a control chart for TV sets. For the past several days, a total of 200 TV sets were inspected and a total of 300 nonconformities found in all of them. They decided to use the u-chart for the number of nonconformities per item with the inspection unit consisting of 4 TV sets. a) What should the center line and upper and lower control limits be if they want to stick to the standard choice of L- 3?
b) What is the in-control ARL of this chart? Reminder: the distribution of the number of nonconformities per item is not Poisson, but that for the total number of nonconformities in the inspection unit is.
c) What is the out-of-control ARL if the average number of nonconformities changes to 3 per item?