Business Statistics

Chapter 17 | Statistical Quality Control 671

defectives per sample whereas c chart graphs the number of defec-

tives per item or unit. np chart is used to control the actual number of

defective items in a sample when the sample size is constant.

In some cases, statistical process control is neither viable nor de-

sirable. In these cases, acceptance sampling is used for quality con-

trol check. In acceptance sampling, a sample is selected from a lot or

batch. On the basis of the information obtained from the sample, a

lot or batch is accepted or rejected. In general, acceptance sampling

plans can be broadly classified into three categories: single-sample ...