Back to matchesWe found a matchYour institution may have access to this item. Find your institution then sign in to continue.TitleStatistical Note.AuthorsJOHNSTON, J.PublicationManchester School (1463-6786), 1956, Vol 24, Issue 1, p45ISSN1463-6786Publication typeArticleDOI10.1111/j.1467-9957.1956.tb00974.x