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Epidemiology:
doi: 10.1097/EDE.0b013e3182126442
Letters

Distributing Surveys: Postal Versus Drop-and-collect

Maclennan, Brett; Langley, John; Kypri, Kypros

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Injury Prevention Research Unit, Department of Preventive and Social Medicine, University of Otago Dunedin, New Zealand (Maclennan, Langley)

Injury Prevention Research Unit, Department of Preventive and Social Medicine, University of Otago, Dunedin, New Zealand School of Medicine and Public, Health University of Newcastle Australia (Kypri)

Supported by an Accident Compensation Corporation Postgraduate Scholarship (to B.M.). The project was funded by the Health Research Council and the Alcohol Advisory Council of New Zealand.

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To the Editor:

The continuing decline in household survey response rates is a concern for the health and social sciences, primarily because of the increasing risk for selective nonresponse to bias estimates of prevalence and other parameters of interest.1 Household surveys involving face-to-face interviews typically yield higher response rates than postal and telephone surveys, but they are relatively expensive and prone to bias from interviewer effects and socially desirable response.2

The drop-and-collect method may reduce the risk of bias from nonparticipation, interviewer effects, and social desirability effects, by harnessing the benefit of face-to-face recruitment and follow-up while leaving participants to complete the survey alone and in their own time. Some studies suggest that response rates may be higher for drop-and-collect than postal surveys,3–5 but there have been no randomized studies.

In the piloting of a public-opinion survey for a study in New Zealand,6 we conducted a randomized comparison of a standard postal survey method versus a drop-and-collect method. The aims were to determine whether drop-and-collect would produce a difference in response, and to examine differences in participants' answers by method of delivery.

In 2007, we randomly selected from the electoral roll 100 people (mean age, 51 years) who resided in the town of Alexandra (population 4800), and randomized 50 to each group. Common to both groups was a survey pack containing a 12-page questionnaire, an invitation letter, a study information sheet, and a stamped return envelope.

The sample size of 100 (50 per group) could detect a large difference in response (eg, a 50% and 80% response for postal and drop-and-collect methods, respectively). Given our limited resources and the wide geographical dispersion of communities and residents in the main study, a large difference was considered necessary to justify the costs of using the drop-and-collect method.

On day 1, the postal group subjects were sent the survey pack, and on day 14 those who had not responded were sent a reminder letter. On day 28, a replacement survey pack was sent to nonresponders. The drop-and-collect group was visited by one of us (B.M.) on days 3–8, given a survey pack and invited to participate. Up to 3 visits were made to each household to invite participation. In 3 cases, no contact was made, and the survey pack was left in the sample member's mailbox.

The results are summarized in the Table. The difference in response rates was 9% (for drop-and-collect, 36/50; postal, 31/49). There were also differences in sex and age distributions, drinking levels, and opinions on alcohol policy, but the small sample sizes limit these estimates.

Table 1
Table 1
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The cost per respondent for the drop-and-collect method was approximately double that for the postal survey. However, it should be noted that cost estimates are highly sensitive to factors such as the distance of the study sites from the research center, geographic density, and whether local staff can be employed. Much of the cost of drop-and-collect arose from return travel to the study site (Alexandra is 190 km from the research center) and accommodation.

While our findings did not justify using the drop-and-collect method in the context of our main study, the option deserves further investigation. It may be particularly useful in well-enumerated study populations in high-density areas, where transport to population centers is inexpensive or where survey team members can be employed in the study sites. In situations where a postal survey elicits only a moderate response (eg, ∼50%), the extra 10%–15% that may be gained using the drop-and-collect method might meaningfully reduce nonresponse bias.

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ACKNOWLEDGMENTS

We thank Luke Wolfenden of the University of Newcastle for reviewing a draft of the manuscript.

Brett Maclennan

John Langley

Injury Prevention Research Unit

Department of Preventive and Social Medicine

University of Otago Dunedin, New Zealand

Kypros Kypri

Injury Prevention Research Unit

Department of Preventive and Social Medicine

University of Otago

Dunedin, New Zealand

School of Medicine and Public

Health

University of Newcastle Australia

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REFERENCES

1. Caetano R. Non-response in alcohol and drug surveys: a research topic in need of further attention. Addiction. 2001;96:1541–1545.

2. Dillman DA, Smyth JD, Christian LM. Internet, Mail, and Mixed-Mode Surveys: The Tailored Design Method. 3rd ed. Hoboken, NJ: Wiley & Sons; 2009.

3. Steele J, Bourke L, Luloff AE, Liao PS, Theodori GL, Krannich RS. The drop-off/pick-up method for household survey research. J Community Dev Society. 2001;32:238–250.

4. Brown S. Drop and collect surveys: A neglected research technique? Mark Intell Plan. 1987;5:19–23.

5. Stover RV, Stone WJ. Hand delivery of self-administered questionnaires. Public Opin Q. 1974;38:284–287.

6. Maclennan B. A. Local Government Alcohol Policy: Community Sentiment and the Policy Development Process [doctor of philosophy thesis]. Dunedin, New Zealand: University of Otago; 2010.

7. Saunders JB, Aasland OG, Babor TF, de la Fuente JR, Grant M. Development of the alcohol use disorders identification test (AUDIT): WHO collaborative project on early detection of persons with harmful alcohol consumption–II. Addiction. 1993;88:791–804.

© 2011 Lippincott Williams & Wilkins, Inc.

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