In a press release and a five-page letter to the scientific community, Peter Kim asserts that although Merck had to correct a statistical method, the 18-month conclusion is still valid based upon the data Merck had at the time.
Anyone seeking definitive advice on which method is best will, I fear, be disappointed by the chief inspector's conclusion that "there is no clear statistical link between the extent of setting in schools and the attainment of pupils".