In a typical A/B test, how are participants allocated to variants?

• A. A random 50% split between the two variants
• B. Based on user location
• C. Based on device type
• D. Fixed 60/40 split

Answer: (A)

In a typical A/B test, participants are assigned to the two variants randomly, usually with about half seeing each version. This randomization makes the groups comparable on both observed and unobserved factors, so any difference in outcomes can be attributed to the variant itself rather than who the users are. A 50/50 split also maximizes statistical power by keeping the group sizes equal, which helps detect real effects more reliably. Allocating by location or device would introduce confounding factors, since differences in results could reflect user characteristics rather than the variant. A fixed or uneven split might be used in special cases, but the standard approach is a random, roughly equal allocation.