Chance, on purpose
A computer or a numbered system assigns people to groups by chance. The aim is to spread differences, such as age or habits, evenly, so the comparison is fair and no one can nudge it.
Why not just choose
If a person picked the groups, even with good intentions, they might place certain people together without noticing. A chance process takes that out of human hands.
Not all groups are equal in size
Some studies give more people the new approach than the comparison. The listing may mention an allocation ratio such as 2:1, which is only a description of the split.
The takeaway
Randomization is about the fairness of the study, not about anyone’s luck. If you read a listing and want to understand how assignment works, the study team can explain the method used.
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