A federal agency responsible for enforcing laws concerning weights and measures routinely inspects packages to determine whether the weight of the contents is at least as great as that advertised on the package. A simple random sample of 25 observations of a product whose container claims that the net weight is 10 ounces yielded a mean of 9.48 ounces and a variance of 1.43 ounces. Do these data provide sufficient evidence to enable the agency to conclude that the true mean net weight is lower than the net weight indicated on the container? Use =0.05. Give the conditions under which this test is valid.