20 CHAPTER 3 REVIEW OF CONJOINT ANALYSIS THEORY ...

letter A and a follow-up questionnaire were sent two weeks after the initial mailings. The
letter served two purposes, (1) it thanked the individuals who had responded, and (2)
reminded those who had not responded to do so as soon as possible because their
participation are important for success of the study.
One difficulty with mail questionnaires, is that not all respondents will answer all
questions. Sections will be left unanswered resulting in incomplete questionnaires that
cannot be used in the analysis. In addition, surveys will be “ not deliverable” because of
“incorrect addresses”. Responses were received from 524 (15 % of sample) individuals.
However, not all of the returned surveys were completed. Only 509 respondents returned
a completed questionnaire for a 14.75 % useable response rate. Of the initial sample of
3450 surveys, nine were undelivered.
Model Specification
Evaluation and measurement of product profiles in conjoint studies usually
involves using either a metric scale or a non-metric scale to elicit consumer preferences.
Methods that assume the dependent variable is of an ordinal scale are ranked ordered
because they provide a non-metric ordering of respondents’ preferences. The interval
rating method is used when metric measures of respondents’ preferences are obtained.
The ranking format allows respondents to rank product profiles from most preferred to
least preferred. The rating format asks respondents to indicate their preferences for
several hypothetical products, which could results in two or more products receiving the
same score. This ability to express order, indifference and intensity for different product
profiles, allows for both cardinal and ordinal properties of utility to be examined.
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