1. The masses of compartments produced by a certain machine are normally distributed with mean 15.4 g and standard deviation 2.3 g. The setting on the machine is altered, following which a random sample of 81 components is found to have the mean mass of 15.0 g. Does this provide evidence, at 5% significance level, of a reduction in the mean mass of components produced by this machine? Assume that the standard deviation is not altered.