FWER, or Family-Wise Error Rate, is a term commonly used in statistical analysis, but its principles can be applied to email marketing to optimize campaign performance. In the context of email marketing, FWER can be understood as the probability of making one or more Type I errors (false positives) among a set of hypothesis tests. Essentially, it's about reducing the chances of wrongly assuming that a particular change or element in your email strategy is effective when it is not.