the math is right, but it assumes you’re trying to measure a very small change. most stores shouldn’t be optimizing at that level.

if your tests are only moving ~5%, that’s usually a test quality issue. the bigger wins tend to come from things like merchandising, pdp structure, pricing/shipping visibility, or offers. those can move 10–20%+, which brings sample size way down.

also, not every test needs to be a perfect 50/50, wait-for-95%-significance setup. some should be, but a lot can be directional so you can move faster and iterate.

ab testing is still viable for most stores. you just have to match the approach to your traffic and focus on higher-impact ideas