An experiment with an advance letter of an interview inquiry.

In an earlier study (Cartwright and Tucker, 1967) we explored the possibility of reducing the number of calls on an interview inquiry by writing to people beforehand asking when they were most likely to be in. That experiment was unsuccessful: more people replied saying that they did not want to be interviewed than wrote telling us suitable times to call, and the final response rate in the experimental group who were sent letters was lower than in the control group who were not. Advance letters which simply inform people about the study and do not ask for any reply may have a different effect. To test this we decided to try to assess the effect of an advance letter on the response rate in our next study.