Page 77 - Design for Six Sigma for Service (Six SIGMA Operational Methods)

58 Chapter Four

Mail-Out Surveys
The mail-out survey involves mailing printed questionnaires to a sample of
predesignated potential respondents. Respondents are asked to complete the
questionnaire and mail it back to the survey researcher.

The advantages of the mail-out survey include the following:
1. Low cost: Other survey techniques require trained interviewers, and
in-person interviews may incur high travel costs.
2. Convenience: The questionnaire can be completed at the respondent’s
convenience.
3. Privacy: Because there is no personal contact, the respondents may
feel more comfortable and their privacy is preserved.
4. Lack of time pressure: The respondents can take their time to complete
the questionnaire and consult their personal records if necessary.

The disadvantages of the mail-out survey include the following:
1. Lower response rate than with other methods: The mail-out survey
response rate usually ranges from 20 to 30 percent in the worst case to
85 to 90 percent in the best case. Therefore, an adequate number of
mail-out questionnaires and many follow-ups are needed to achieve
the desired sample size.
2. Comparatively long time period: Questionnaires from the mail-out
survey usually take a few weeks to be returned.
3. Self-selection: The survey researcher only receives the returned ques-
tionnaires. The people who choose to fill out and return the ques-
tionnaires may not adequately represent the population. For example,
people who have low reading and writing proficiency may never return
their questionnaires; thus they will not be represented in the sample.

In-Person Interviews

In-person interviews are conducted by an interviewer who talks directly to
respondents to get the information.

The advantages of the in-person interview include the following:
1. High response rate: The response rate of the in-person interview is
much higher than that of mail-out surveys.
2. Ability to contact hard-to-reach population: Certain groups are
difficult to reach by mail or telephone; the in-person interview is the
only way to reach them.