Learn the techniques to get as many responses as possible to your survey.
For the mailed survey there are several tactics you can employ to increase the response rate. Write a letter of transmittal stating the purpose and importance of the study, the reason why the individual was selected to participate, insurance of confidentiality, and an offer of thanks for the individual's participation. If a separate letter is not appropriate, then consider a survey coversheet that contains similar information. Another technique is to send out a mailing informing intended participants that a questionnaire is forthcoming. Advance notification informing individuals they have been selected for your survey may also spark supportive interest.
Sending the Survey and Following Up
Always pick a date for respondents to reply, and be sure that date is at least a few weeks after the survey is mailed. Otherwise you'll spend most of your time waiting for a response that will never come. About two weeks after your initial mailing, send a follow-up letter. In the letter thank those who have responded and indicate the necessity of obtaining outstanding surveys. Sometimes a statement like "If you have lost the original survey, please contact (researcher's name, address, phone/fax number) and a new survey will be sent immediately" may also be helpful.
How many follow-ups are required?
That number is up to the researcher. If you can complete your research with a 20% response rate and your sample represents the population from which it is drawn, then don't follow up. Do be prepared to explain in your report why you stopped. Some researchers will attempt as many as three times to gain subject participation. Given that you have had a particular number of responses now, ask yourself, "Would my results be different if everyone responded?" If you had a 90% initial response, it is unlikely that the remaining 10% would disrupt your findings. If the initial response was only 10%, then you have a considerable amount of work ahead of you.