Apparent validity of alternative survey methods.

A comparison of results using three methods of obtaining the same survey data is reported. The assumption is made that in relation to a question for which there is a socially desirable response, e.g., use of seat restraints for children, those reporting nonuse or infrequent use are giving truthful answers. In an experiment in health education, follow-up assignments were made randomly, one third being interviewed face-to-face, one third by telephone, and the rest by a postal questionnaire. There were no significant differences by method of follow-up in the scores reflecting reported changes in behavior following instruction. Both the telephone and mail methods, however, appear to yield a higher proportion of "truthful", i.e., socially undersirable, responses; 30.4% of those contacted by telephone admitted to not using a restraint on the last trip, compared with 26.3% of those questioned by mail and 17.5% in a household interview. It is recommended that careful consideration be given to these alternative methods of obtaining data, particularly in view of their lower cost and possibly greater validity.