Including a 'None of the Above' button in your Conjoint Rank survey allows respondents to show when they would not consider any of the profiles in a voting set sufficient or appealing to them:
The data from this 'None of the Above' button appears throughout your Conjoint Analysis charts on the results dashboard, but there is one chart that is specifically designed for analyzing this opt-out data → the Rejection Rate chart.
The Rejection Rate chart splits out each conjoint option separately and looks at how often the 'None of the Above' button was picked when the respondent could have chosen a profile containing that option instead.
For example, on the example above, iPhone has a rejection rate of 3%, meaning that in 100 voting sets where the 'iPhone' option was visible for the Brand category on at least one of the two profiles, the respondent chose 'None of the Above' 3 times instead of a profile.