``STUDENT'S'' letter in NATURE of December 5 shows that he has overlooked the purpose of the paper he criticizes, although it was set out in the first sentence of the summary as follows : ``This enquiry was carried out to test the truth of the opinion expressed by `Student' that randomization achieves its object `usually at the expense of increasing the variability when compared with balanced arrangements', and that one of the means available to experimenters of reducing the error is by adopting `a regular balanced arrangement'.''