In the production of low-pressure gas cylinders a lathe operator has to take the bottom and top parts of a cylinder, tit them with a footling and a collar, and then weld the halves together. An experiment was conducted to investigate the time taken lo complete this process. Two different lathe designs were considered, and three skilled operators were used in the experiment. Six completion times were measured for each operator using both of the lathe designs. The times in seconds are given in DS 14.3.6. Is there any evidence of a difference in the efficiencies of the two lathe designs? Is the difference in the efficiencies of the two lathe designs the same for each of the operators?