In a study of copper deficiency in cattle, the copper values (mg/100 mL blood) were determined both for cattle grazing in an area known to have welldefined molybdenum anomalies (metal values in excess of the normal range of regional variation) and for cattle grazing in a nonanomalous area ("An Investigation into Copper Deficiency in Cattle in the Southern Pennines," J. Agric. Soc. Cambridge, 1972: 157-163), resulting in s1 = 21.5 (m = 48) for the anomalous condition and s2 = 19.45 (n = 45) for the nonanomalous condition.

Is there a difference in the average level of the pollutant of the two sites?