Weighted random draws explained

What weighting means

A weighted draw gives each entry a different probability. If entry A has weight 2 and entry B has weight 1, A is twice as likely to be selected. The total weight is 3, so A has a 2/3 chance and B has a 1/3 chance.

The visual wheel should match the maths. In WheelBloom, weighted entries produce larger slices. If the slice sizes and the odds disagree, the tool is lying to the room.

When unequal odds are fair

Weighting is legitimate when the underlying chances really are unequal, and everyone knows it before the draw:

• Prize inventory. You have ten small prizes and one grand prize. The small prizes can appear more often.
• Availability. One volunteer is available for two shifts and another for one. The draw can reflect the slots rather than the people.
• Deliberate quotas. A survey draw needs a fixed mix of regions or roles. Weighting by quota is a sampling method, not a trick.

In each case, the weights represent a real constraint. Write the constraint down before the spin so the result can be explained.

When weighting is unfair

Weighting is unfair when it silently changes a draw that was advertised as equal. A raffle, a classroom name picker, and a giveaway winner are usually expected to be equal-odds. If you weight them without saying so, you have changed the deal.

It is also a bad idea to weight by preference. Giving a friend a higher weight is not randomness with a nuance; it is a rigged draw.

How to set weights in WheelBloom

Turn on Weighted entries. Add a suffix to a line: Grand prize x1, Small prize x5. The number is the relative weight, not a percentage. A weight of 5 is five times as likely as a weight of 1.

Decimals work too: Volunteer A x1.5. The wheel rounds the display but keeps the relative odds. Turn weighted mode off to return every entry to equal odds.

Show the odds, not just the wheel

The entry list is visible beside the wheel for a reason. For a public draw, read the weights aloud or show the list before the first spin. If the audience cannot see the weights, they cannot judge whether the draw was fair.

For a recorded stream or a live event, capture the list before the spin and the winner after. A short record prevents most disputes.

Do the maths before the draw

Add up the weights and check the resulting chances. If an entry has a weight of 90 out of 100, the draw is effectively a formality. That may be intentional for a prize inventory, but it should not be described as a fair chance for everyone.

When in doubt, use equal weights. Weighted mode is for genuine inequality, not for making a result more exciting.

Read how the draw works or open the wheel of names to try it.