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