Your answer should focus on describing the difference between A/B and multivariate testing. Whether or not you've used this type of performance testing before, you should go into the interview with knowledge about how it works.

"Testing the effectiveness of email campaigns is an essential part of marketing. A/B testing looks at one component of the email, while multivariate testing looks at several variables at once. For example, an A/B test could be set up to send out two versions of an email to two separate groups of customers with the only difference being the subject line. The open rates of the emails would show which subject line was more effective. In multivariant testing, one version of the email would have several varied components. One could have a simple template and a single call to action. The other would use a busier template and two calls to action."