Quality control investigator: Upon testing samples of products from our supplier that were sent by our field inspectors from various manufacturing locations, our laboratory discovered that over 20 percent of the samples were defective. Since our supplier is contractually required to limit the rate of defects among items it manufactures for us to below 5 percent, it has violated its contract with us.
The reasoning in the quality control investigator's argument is flawed in that the argument overlooks the possibility that the field inspectors tend to choose items for testing that they suspect are defective.