Introductory postcards: do they increase response rate in a telephone survey of older persons?

The purpose of this study was to assess whether contact by mail via an introductory postcard would increase the response rate to a telephone survey in a selected population of 348 people 60 years and older. Of this group, 208 were sent a postcard introducing the study and informing them that someone would call in the next 1-2 weeks to conduct a telephone interview. The remaining sample of 140 did not receive the introductory postcard. Amongst the potential participants who were contacted and able to participate (n = 240), the response rate for completed interview was 58.0% for those sent a postcard and 42.3% for those who were not. The refusal rate was 25.3% (postcard sent) and 37.2% (not sent a postcard). When the outcome of contact is collapsed to two categories, 'agreed to participate' and 'refusal', the response rate to participate was 73.5% (sent a postcard) and 59.0% (not sent a postcard) (chi(2) 5.14, d.f. 1, sign. 0.023). The response rate amongst those who recall being sent a postcard rose to 86.0%. Whether agreeing to participate or refusing to be involved in the survey was dependent on being sent an introductory postcard. The conclusion is that mailing a postcard prior to the first telephone contact increases the participation rates of older persons in a telephone survey at very little extra cost (A$0.60 per person).