HubSpot and CRM data: Hands-on experience pulling and analyzing HubSpot data (contacts, custom objects, properties, lifecycle stages, lists, marketing email, forms, and subscriptions) through reports, exports, or the API, and an understanding of the limits of email engagement metrics (such as the effect of Apple Mail Privacy Protection on open rates). Experimentation and statistical testing: Experience designing and evaluating A/B tests, including correctly applying statistical tests (two-proportion z-tests, t-tests, and chi-square tests), power analysis, sample-size calculation, and confidence intervals, and avoiding pitfalls such as stopping tests early and multiple comparisons.