Question

The chemical composition of soil varies with depth. Fifty specimens were each taken at depths 50 and 250 cm. At a depth of 50 cm, the average NO3 concentration (in mg/L) was 88.5 with a standard deviation of 49.4. At a depth of 250 cm, the average concentration was 110.6 with a standard deviation of 51.5. The 95% confidence interval for the difference in NO3 concentrations at the two depths is nearly

a) (10.3, 44.9)

b) (9.3, 48.9)

c) (2.3, 41.9)

d) (0.3, 44.9)

Answer 1