When equal probability is the clearest rule
Use equal probability when every entry has the same status and there is no relevant reason to prefer one over another. Classroom participation, presentation order, party games, and choosing between acceptable dinner options often fit this rule.
With five active options, each option has a 1 in 5 chance, or 20%. Removing one result changes the next draw to four active options at 25% each.
When weights are justified
Weights make sense when the unequal chance represents a real rule established before the spin. Examples include testing common and rare software scenarios, rotating tasks toward overdue items, or modeling prize tiers where the quantities are known.
Weights should not be used to quietly favor a preferred person. If a result affects other people, show the weights and explain why they exist before spinning.
How to calculate a weighted chance
Add the active weights, then divide one option’s weight by that total:
probability = option weight ÷ total active weight
If three options have weights 6, 3, and 1, the total is 10. Their chances are 60%, 30%, and 10%. The weights could also be 60, 30, and 10 or 12, 6, and 2; the proportions are the same.
Weights are not percentages
Weights do not need to add up to 100. A weight of 4 does not automatically mean 4%. It means four relative units compared with the other active weights. The displayed percentage is calculated from the complete active list.
Common mistakes
- Assuming a larger visual segment guarantees a result within a small number of spins.
- Leaving an option at zero weight and expecting it to remain selectable.
- Giving duplicate entries separate weight without intending to.
- Changing weights between spins without telling participants.
- Using subjective weights for a decision that requires objective evidence.
A simple decision rule
If you cannot give a clear reason for unequal chances, use an equal wheel. If unequal chances are the point of the exercise, write the rule down, display the resulting percentages, and use the Weighted Wheel.