Many researchers have found that prenotification mailings can increase the effectiveness of surveys. Prenotification mailings are used for initial contact with survey participants, not only in the mail survey but also in other survey modes, like telephone and online surveys. The use of prenotification ensures that respondents don’t unintentionally ignore or disregard the survey. Moreover, it fosters trust from participants by proving the authenticity of the study. 

Benefits of Prenotification Letters

1. Increase in Survey Response Rate

There are debates on whether or not prenotification mailing helps increase survey response rates. Early studies have shown that prenotification mailings can positively affect survey response rates in mail surveys. In 1983, Yu and Cooper found that the response rate increased by 8%, while a 1991 study by Yammarino, Skinner, and Childers showed a response rate increase of 28.5%. 

Studies in Telephone survey also show an increase in response rates: The Cost-Effectiveness of Alternative Advance Mailings in a Telephone Survey

In 2005 the Office for Survey Research (OSR) experimented with comparing advanced letter mailing versus postcard effectiveness. The results showed that prenotification letters result in better response rates than postcards. While the latter results in better response rates than not doing any prenotification.

Similarly, another study, “The Influence of Advance Letters on Response in Telephone Surveys: A Meta-Analysis”, reviewed studies on the effect of prenotification mailings to increase telephone survey response rates. The research found that advance mailings are an effective tool in telephone surveys since response rates increased to 8% when advance letters were used. 

With web surveys, a 2011 study entitled, Effects of Incentives and Prenotification on Response Rates and Costs in a National Web Survey of Physicians, as well as a recent 2018 study, “Effects of pre-notification, invitation length, questionnaire length and reminder on participation rate: a quasi-randomised controlled trial”,  confirmed that prenotification letters increased survey response rates. 

2. Increase in Survey Response Speed

Some research found that although prenotification mailings do not increase response rates, they still positively affect the effectiveness of the survey: An earlier study in 2013 found that the groups that received prenotification mailings returned their questionnaires faster:  Prenotification letter increased initial response, whereas sender did not affect response rates.  The same result was determined in an earlier study, “Effect of Pre-Notification on Mail Survey Response Rates: An Experimental Result”, wherein prenotification increased response speed. 

3. Increase in Consent to Link Survey Data to Existing Survey Data

Another positive impact of pre-notification mailings is that it can increase the probability that respondents give consent to link their survey data to existing survey data: Pre-notification letter type and response rate to a postal survey among women who have recently given birth. 

Ultimately, the use of prenotification mailings should be weighed carefully with the available resource and needs of the survey project. It can be a helpful tool in planning and implementing effective surveys. That being said, below are the key features and tips in creating a prenotification mailing:

1. Include the purpose or objective of the study. 
2. Identify Sponsors. Use branded letterhead. Studies have found that highlighting credible sponsors of the research can increase survey response rates. It adds credibility to the study as well as encourages participants who are fond of the sponsors; for example, participants coming from the same university.  
3. Emphasize the personal benefit respondents will receive from the survey, whether it’s altruism or a good incentive. 
4. Enlighten participants about the benefit that will come from the survey results.
5. Contain an original signature from an identifiable person (in contrasting color), and send in a branded envelope.

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