The manager at Big Package Express knows that in the past, the packages the company handled had a mean weight of 36.7 kg. A random sample of last month's shipping records yielded a mean weight of 32.1 kg for 64 packages. Assume that the standard deviation of package weights is 14.2 kg, and that the package weights are approximately normally distributed. Does the sample result tell us that the average weight of the packages has decreased?