It is expected that a certain procedure for estimating the percentage amount of a substance X in a sample of material will give a standard error approximately equal to 0-12. Two chemists take samples from a given bulk of material and each performs five independent determinations of the percentage amount of X present in the material. Their readings are as follows: 2-43, 2-42, 2-22, 2-29, 2:06 First chemist: Second chemist: 2-48, 2-72, 2-43, 2-40, 2.58 Do these figures support the assumption that the standard error of a determination is 0-12? Is there any evidence that one chemist's readings are biased relative to the other? (Camb. N.S.)