Question

The local newspaper receives several complaints per day about typographic errors. Over a seven-day period, the publisher has received calls from readers reporting the following total daily number of errors; 4, 3, 2, 6, 7, 3, and 9. Based on these data alone, what type of control chart(s) should the publisher use?

Answer 1

Ans. C-chart should be used in this case.

C-chart shows how the process, measured by the number of non-conformities or defects per unit of an item, changes over time.

c = total number of defects/total number of samples

UCL = c+k√c

Center Line = c

LCL = c-k√c

This gives an idea of non-critical level of non-conformity.