A laboratory claims that the mean sodium level, μ, of a healthy adult is 139 mEq per liter of blood. To test this claim, a random sample of 100 adult patients is evaluated. The mean sodium level for the sample is 142 mEq per liter of blood. It is known that the population standard deviation of adult sodium levels is 12 mEq. Can we conclude, at the 0.05 level of significance, that the population mean adult sodium level differs from that claimed by the laboratory?