Should you include the “None of the above” option?
For your conjoint experiment, you can choose one of three options that characterise your product. This will affect how the “None of the above” option is presented to respondents and how analytics is run on the data we collect.
1. Normal product that customers routinely buy
2. Product that customers are forced to buy
3. New product that customers are not used to buying
Examples
FMCG/CPG, education, personal services. The vast majority of products fall into this category.
Critical medication or government services.
Start-ups with new business models.
When to use
This option should be in most marketing studies should because it reflects actual market behaviour of not buying a product.
This option is suitable to medical studies should because it reflects doctors’ and patients’ lack of “opt-out” options.
When consumers are not used to buying this product 😊
How it works
Respondents will be able to select a “None of the above” option, which will be part of the choice set.
When such products are studied, respondents will not be able to select a “None of the above” option. This is technically known as a “forced choice response”.
With such products, respondents will first be forced to choose an alternative, and then they will confirm if they would buy it at all. This is technically known as a “two-stage response”.
In analysis
In addition to relative preference scores for all levels tested, a utility value will be computed for "None" that will measure respondents' tendency to select none of the alternatives. All simulations will include a preference for "None of the above".
No utility value is computed for None, and simulations do not include a "None of the above".
Despite the different user experience, this method is analytically identical to the normal none. In any choice task where the respondent indicates they would not choose the product in the dual-response, they are recorded as selecting none. A utility value for "None" is computed, and all simulations will include a "None of the above".
Why do these options depend on product types?
Consumers tend to think twice when it comes to buying new products. Therefore the chance of not buying any product in new categories is higher. This needs to be reflected in conjoint analysis as well.
The table below shows the percentage of “none of the above” responses for a sample of 709 experiments with two-stage response and 4863 experiments with the standard “none of the above” option (including both generic and brand-specific conjoint studies). It is split by type of response and by country (listing only top 12 countries of respondents):
Country
Standard response (normal products)
Two-stage response (new products)
% of “None of the above”
Number of choice sets
% of “No”
Number of choice sets
United States
14%
1,500,371
18%
269,830
United Kingdom
9%
392,662
25%
16,303
Mexico
16%
248,873
Insufficient data
Germany
14%
206,879
Insufficient data
Canada
18%
129,778
18%
21,593
China
6%
136,844
Insufficient data
Netherlands
15%
130,807
Insufficient data
France
13%
124,528
Insufficient data
Australia
14%
111,837
27%
20,188
Brazil
8%
89,825
32%
13,123
India
8%
89,034
Insufficient data
Russia
18%
85,293
Insufficient data
All (including those not listed above)
13%
4,013,278
19%
476,427
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