In data science, A/B testing is a controlled experiment method for comparing two (or more) variants of a product to see which performs better. Typically, a control (A) and one or more variations (B, C, …) are served at random to users, and their key metrics (e.g. click-through or conversion rates) are recorded. By using statistical tests on these results, we can decide which version delivers a meaningful improvement. In this post, we’ll dive deep into A/B test design and analysis. We’ll cover hypothesis formulation, randomization, sample size and power, statistical significance, and common pitfalls – with references from recent industry and academic sources. The goal is a rigorous, reproducible approach to experimentation that experienced data scientists can adopt.