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The cover letter or email invitation is an essential part of the survey. To a large degree, the cover letter will affect whether or not the respondent completes the questionnaire. It is important to maintain a friendly tone and keep it as short as possible. The importance of the cover letter should not be underestimated. It provides an opportunity to persuade the respondent to complete the survey. If the questionnaire can be completed in less than five minutes, the response rate can be increased by mentioning this in the cover letter.

Flattering the respondent in the cover letter does not seem to affect response. Altruism or an appeal to the social utility of a study has occasionally been found to increase response, but more often, it is not an effective motivator.

There are no definitive answers whether or not to personalize cover letters (i.e., the respondents name appears on the cover letter). Some researchers have found that personalized cover letters can be detrimental to response when anonymity or confidentiality are important to the respondent.

The literature regarding personalization are mixed. Some researchers have found that personalized cover letters with hand-written signatures helped response rates. Other investigators, however, have reported that personalization has no effect on response.

The signature of the person signing the cover letter has been investigated by several researchers. Ethnic sounding names and the status of the researcher (professor or graduate student) do not affect response. One investigator found that a cover letter signed by the owner of a marina produced better response than one signed by the sales manager. The literature is mixed regarding whether a hand-written signature works better than one that is Xerox copied. Two researchers reported that copied signatures worked as well as a hand-written one, while another reported that hand-written signatures produced better response. Another investigator found that cover letters signed with green ink increased response by over 10 percent.

It is commonly believed that a handwritten postscript (P.S.) in the cover letter might increase response. One older study did find an increase in response, however, more recent studies found no significant difference.

When sending an email invitation, it is very important that you check the email content for it's spam rating. Most people have spam filters installed on their computers, and poorly written invitations will never be seen by the intended recipient. There are many free online spam checkers (type "check email spam rating" into one of the search engines).

The general components of a cover letter or email invitation are:

1. Describe why the study is being done (briefly) and identify the sponsors.

2. Mention the incentive. (A good incentive is a copy of the results).

3. Mention inclusion of a stamped, self-addressed return envelope (written surveys).

4. Encourage prompt response without using deadlines.

5. Briefly describe your "confidentiality/anonymity" policy.

6. Give the name and phone number and/or email address of someone they can contact with questions.


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