Evaluation of Differences in Giving and Volunteering Data Collected by In-Home and Telephone Interviewing

While preparing for its 1999 study, Giving and Volunteering in the United States, Independent Sector was told by its contractor that starting in 2000, it could no longer conduct the survey using in-home interviews. Independent Sector contracted with another company to do a parallel study in 1999 by telephone to identify issues related to changing the survey mode. The results showed highly statistically significant differences on many of the major questions, raising questions as to whether the differences were mainly due to between-company or between-collection modalities. Another company was then commissioned to do both an in-home study and a telephone study in two cities in New England. With similar training for all interviewers, better sampling methods, prior letters to potential respondents, incentives, and multiple follow-ups, the results showed no significant differences between modes on any of the major questions.