This Instructional Activity is a part of the Lesson 15, Unit 4, Grade 7. This activity uses a quality control situation to work with percent error. It is very common that products in a factory are checked to make sure that they meet certain specifications. In this case, boards are cut to a specific length. If they are too long or too short they are rejected. Students should make sense of the decision to be based on percent error and not on measurement error.