Random Sampling by Telephone— An Improved Method

Conventional telephone directory sampling techniques fall short of producing a perfect sample of domestic telephone subscribers. Near the end of the 1963–64 local telephone directory year, when the number of new, but as yet unlisted, telephones was at its maximum, 18 percent of private telephones in use in the Greater Cincinnati area were not listed in the current directory. By means of a new technique for obtaining numbers, one large source of sampling error can now be virtually eliminated in sampling private telephone subscribers, whether listed or not.