Answer Happy

1. (15 points) In a packing plant, a machine packs cartons with jars. It is suspected that an old machine is less stable than a new machine in the sense that the packing time of the old machine tends to have a significantly larger variance. To assess this claim, the times (in seconds) it takes each machine to pack twenty cartons are recorded, and summary statistics are shown in the table below. Sample size Sample mean 20 Old machine New machine 42.657 41.782 Sample variance 0.918 0.393 20 Test the hypothesis Ho: oso against Ha: o>o, where of is the variance of the packing time of the old machine, and is the variance of the packing time of the new machine. The packing times are assumed to be normally distributed. Use a significance level of a = 0.05.