Editing Conjoint analysis (section)

== Conjoint design ==
A product or service area is described in terms of a number of attributes. For example, a television may have attributes of screen size, screen format, brand, price and so on. Each attribute can then be broken down into a number of levels. For instance, levels for screen format may be LED, LCD, or Plasma.

Respondents are shown a set of products, prototypes, mock-ups, or pictures created from a combination of levels from all or some of the constituent attributes and asked to choose from, rank or rate the products they are shown. Each example is similar enough that consumers will see them as close substitutes but dissimilar enough that respondents can clearly determine a preference. Each example is composed of a unique combination of product features. The data may consist of individual ratings, rank orders, or choices among alternative combinations.

Conjoint design involves four different steps:
# Determine the type of study
# Identify the relevant attributes
# Specify the attributes' levels
# Design questionnaire

=== 1. Determine the type of study ===
There are different types of studies that may be designed:
* Ranking-based conjoint
* Rating-based conjoint
* Choice-based conjoint

=== 2. Identify the relevant attributes ===
Attributes in conjoint analysis should:
* be relevant to managerial decision-making,
* have varying levels in real life,
* be expected to influence preferences,
* be clearly defined and communicable,
* preferably not exhibit strong correlations (price and brand are an exception),
* consist of at least two levels.

=== 3. Specify the attributes' levels ===
Levels of attributes should be:
* unambiguous,
* mutually exclusive,
* realistic.

=== 4. Design questionnaire ===
As the number of combinations of attributes and levels increases the number of potential profiles increases exponentially. Consequently, [[fractional factorial design]] is commonly used to reduce the number of profiles to be evaluated, while ensuring enough data are available for statistical analysis, resulting in a carefully controlled set of "profiles" for the respondent to consider.