the weights of salmon grown at a commercial hatchery are normally distributed with a standard deviation of 1.2 pounds. the hatchery claims (treated as h0) that the mean weight of this year’s crop is at least 7.6 pounds. suppose a random sample of 16 fish yields an average weight of 7.2 pounds. is this strong enough evidence to reject the hatchery’s claim at the 5 percent level of significance?