본문/내용
a steel making facility produces 9cm thick slabs. as part of their quality control program, the steel maker track of the average thickness of each slab. the average thicknesses for the last 300 slabs are given in the excel file `assign1.xls`. during a recent PM (preventative maintenance) shutdown, several changes were made to the facility. the first slab produced after the shutdown had an average thickness of 7.19. the production manager is concerned that the maintenance activities have caused a