Flavours or types of conjoint analysis

For those new to the subject of conjoint analysis, it is easy to be misled that there is only one type or version of conjoint analysis (the single type your agency knows or uses). Or to find the total reverse and become bewildered by the number of abbreviations and names, particularly when it's not too clear what the differences are or why one type is used over another - eg ACA, CBC, MPC, ACBC, full profile, stated preference, DCE/discrete choice estimation among others.

Most conjoint analysis studies carried out professionally use Choice-based Conjoint (CBC) or in early times, Adaptive Conjoint Analysis (ACA), and there is a move to newer types such as Adaptive Choice-Based Conjoint (ACBC). However, there are actually many different types or "flavours" depending on the task at hand. 

Choice-Based Conjoint (CBC) is favoured academically and widely used for pricing and brand value studies, ACA has fallen out of favour but is still used for larger more marketing focused work. Other forms of conjoint incorporate Buy-your-own tasks, configurators, menus or take the basic principles and extend them to create tailored designs for specific markets.

The many types or flavours on conjoint analysis and related options can be confusing as to which to use for which projectThere are three core parts involved in conjoint analysis design. Firstly, the product or service needs to be broken down into component attributes and levels. Then, the decision of what is the best way to present options to customers or consumers (product profiles) combined with the decision of which method should be used to find out which product profiles are most preferred (eg choosing, ranking, rating). And finally the decision of which statistical estimation approach to determine the utility value of each attribute and level to the market (also known as part-worths).

These design decisions depend on the number of attributes to be considered, the contact method (online, face-to-face, phone or by post) and time available for the interview. In addition, the different flavours of conjoint analysis each have differing characteristics in analysis.

Choice-based conjoint analysis (CBC) tends to be preferred if the data needs to be more robust, perhaps because of the inclusion of attributes that may interact with each other, or where price is involved. However, CBC is typically limited to 6-8 attributes and needs to be analysed at an aggregate level and then a technique like Hierchical Bayes needs to be used to impute back individual level utilities. Alternatively, if the number of attributes is higher and data is needed at an individual level Adaptive Conjoint Analysis may be of more use. If you run into conjoint analysis as a student, then it is most probably through the use of full-profile conjoint analysis. There are other options such as partial-profile, menu-based, or adaptive choice based conjoint available among a range of other trade-off type approaches depending on the task at hand.

Choice Based Conjoint Analysis- CBC

CBC is the most common form used at the moment. Most commonly CBC is based on a full-profile approach (a level from each attribute is shown in the product profile) but to keep amount of work the respondents need to do to a minum, the set of possible profiles is spread across the sample, so typically each respondent will see 8-12 choice tasks - ie the respondent will be asked to give choices from 8-12 different choice sets.

CBC usually shows more than just two "products" at the same time, together with a none-of-these option enabling more realistic choice decisions to be evaluated. This feature is heavily used in shelf-based displays used to test pricing for FMCG/CPG type products where there may be 30 brands to choose from at the same time in a 'virtual' shopping environment.

The limitation on the amount a respondent can absorb at a time, combined with the rapidly increasing number of "full-profile" combinations that come with large designs mean mean that choice-based conjoint is typically limited to 5-7 attributes (in contrast to 25-30 for ACA). There are what are known as partial-profile methods to get round this limitation,, but their use can be challenging.

An additional twist is that the default is to calculate utilities and importances in CBC across a sample as a whole. To get at individual level estimations relies on techniques such as Hierarchical Bayes analysis to infer back individual values (in ACA utilities and importances are calculate directly for each individual in the sample). For work such as segmentation, this places some limitations on CBC data. However the great benefit is that choice-based studies require far shorter questionnaires (10-20 mins) and can be designed to be purely paper-based if necessary.

The main advantages choice-based conjoint gives you are greater robustness of results - particularly for pricing work, combined with shorter and therefore less costly fieldwork. It is also favoured for it's rigour academically. It also enables comparisons with fixed products or fixed tasks enabling you to test new formulations against an existing gold standard or, in the more specialist form of Discrete Choice Modelling (alternate-specific designs), the end model can be tuned to real world data greatly increasing it's predictive power.

The disadvantages are the lower number of attributes that are possible unless you move to more complex bespoke designs using partial profiles, and the lack of directly valued individual level utilities - although techniques such as Hierarchical Bayes (HB) analysis seeks to remedy this by post-hoc simulation of individual level values. However, if you are looking to use conjoint analysis for clustering or segmentation you will need to be aware of the trade-offs needed to get individual level utility scores.

With increased online research, CBC type approaches are being used with very small number of attributes in very short online surveys

Adaptive Conjoint Analysis - ACA

ACA has fallen out of favour with the wide use and availability of choice-based conjoint. However it remains a common method particularly where there are a large number of attributes to be considered for instance in service design or understanding products with a large number of features such as software.

Although ACA uses the same over-arching principles as CBC, in design, implementation and calculation it is completely different. Whereas CBC has respondents selecting from multiple products described with a full set of attributes, ACA shows descriptions using all two or three of the attributes available and is a pairwise only selection. There is also a relatively long self-explication step that respondents need to complete before coming into the main 'pairs' choice part.

The benefits of ACA are that it allows for a large number of attributes (up to 30) and levels (up to 7 per attribute) to be used. However, ACA does require a computer-based interview and the large number of attributes means that it is common for an ACA interview to last 45 minutes or more. In addition, some of the methods it uses to simplify the task of working out utilities mean that some care is needed in choosing and designing the attributes in order to get reliable results.

Technically ACA is known as a hybrid technique as it contains elements of 'self-explication' followed by the trade-off tasks themselves. ACA itself is produced by Sawtooth Software and can be conducted face-to-face or on-line. Telephone use of ACA is difficult and paper-base questionnaires are not possible.

Discrete Choice Analysis/Discrete Choice Modelling

A more advanced form of choice-based is Discrete Choice Analysis (also known as "stated preference research" or an alternative specific choice-based design). DCA studies are particularly popular for transportation studies looking at modal choice - the preference between a train, car and airline for instance. The main difference from CBC is the inclusion of continuous variables such as price and time. This allows the ability to examine the varying costs of the ticket with varying times taken to travel and so to establish the value of time for the journey. This enables transport economists to make statements like "2cm extra leg room is worth 10 minutes longer journey time or £40 extra fare" or "an extra train every 15 minutes would encourage x% of car drivers to switch to the train".

Shelf-based designs

A particularly specialist form of DCM and CBC comes in the form of shelf-based designs which show a range of products (SKUs) at different prices. The aim being to understand price elasticities within a particular category. These types of pricing method are very commonly used within FMCG/CPG pricing research and can be calibrated against retail audit pricing data.

Full profile

Full-profile is the original form of conjoint and is still in use, though predominantly in the US or for student type learning projects it would appear. Like choice-based conjoint this uses a more limited number of attributes to describe the product or service, but sufficient cards or treatments are shown to one respondent to enable individual level utilities to be calculated. A fractional factorial design is used to specify a fixed set of profiles that need to be shown for analysis. The difficulty is that this does limit the number of attributes quite severely. It's likely to be used with 3-4 attributes, but even at this amount, it might involve ranking or rating of 16-24 product profile cards. These old school studies are still popular for simple, non-computer-based projects and are most common for students learning about conjoint for the first time. This is also the main form implemented by non-specialist online survey software, or offered by SPSS in their conjoint module.

Other forms and formats

Recent developments in conjoint include the Adaptive Choice Based Conjoint (ACBC) method from Sawtooth, which combines elements of a configurator, an adaptive element and choices and Menu-Based Conjoint (MBC). In addition we have our own dobney.com software that allows for a range of other more bespoke research areas where traditional forms of conjoint analysis are lacking or where current designs can seem too difficult from a respondent point-of-view These include emotional association tasks, and repertoire purchasing (where someone is buying a bundle of products across a range of uses), volumetric measurement and improved choice displays such as using sliders or more interactive elements to encourage a fuller participation in the decision making process. Similarly, for international research the presentation of prices in different formats and currencies requires careful consideration.

Deciding which format of conjoint analysis to use

We often find that the choice of the type of conjoint analysis to use depends on a number factors. It's often difficult for someone new to the subject to visualise all the options. The biggest determining factor is the number of attributes, and in cases where there are 6-8 attributes, there can be several options and approaches. We often produce several versions and presentations for illustration to help clients see and understand which form and presentation to use, without compromising the final statistical quality of the survey.

Conjoint design

Conjoint demonstration

For help and advice on carrying out conjoint analysis research and which type of conjoint to use contact our consultants atinfo@dobney.com or phone +44(0)20 7193 6640 or +1 713-983-8700.