Weighted lotteries, also known as weighted raffles, are drawings where some entries have a greater chance of winning than others. Unlike traditional raffles where all tickets have an equal opportunity, weighted lotteries assign different weights or chances to different entries.

For instance, in a scenario where the number of tickets purchased increases a participant’s odds, the system rewards those who demonstrate greater interest or investment.

Similarly, a charity might weight chances based on the amount of donations, incentivizing generosity and potentially increasing the fundraising outcome.

In the corporate world sales teams might use weighted lotteries to motivate employees, with odds reflecting sales performance, thus recognizing and encouraging higher achievement.

How a weighted drawing works

Weighted lottery is a system where entrants are given different “weights” or chances of winning based on pre-defined criteria. For example, an entrant with a weight of 2 has twice the chance of being selected as someone with a weight of 1. Similarly, an entrant with a weight of 3 has three times the chance, and so on.

Technically, in the drawing process the system assigns entries based on the assigned weight value for each participant. For instance, if a participant’s weight is 1, his name will appear once in the drawing pool. If the weight is 2, his name will be included twice, increasing the chances of being selected, and this pattern continues proportionally with higher weight values.

Weighted raffle example

Weighted lottery winners

Faced with the enviable problem of too many students competing for too few places in a prestigious exchange programme, one European high school took a creative and fair approach. They offered 20 lucky students a free one-week visit abroad to their prestigious school. With around 400 hopeful applicants, they needed a fair way of selecting participants. Their solution? A weighted lottery system that ensured academic merit was weighted more in the selection process; while on the other hand all the other students had a change to take part as well, not only the best.

To select winners transparently, the school first established a clear method for calculating each student’s weight. Initially, everyone started with a base weight of 1 point. Additional points were then added based on the number of years they had successfully completed at the school, with one extra point awarded for each year. The breakdown was as follows:

• 1 point: 1st year (basic weight)
• +1 point: 2nd year
• +2 points: 3rd year
• +3 points : 4th year

Furthermore, the school introduced a grading scale to factor in academic performance from the previous semester’s report card:

• GPA 4.0: +2 points
• GPA 3.0-3.99: +1 point
• GPA worse than 3.0: +0 points

The final weight for each student was the sum of the base weight + points for the number of years at the school + the points for their grades, resulting in a possible weight range between 1 and 6.

Weighted drawing tool

To handle the drawing process the school turned to RandomPicker.com, a trusted tool for conducting random weighted lotteries. They drew names for the 20 available spots and selected an additional 10 alternates.

RandomPicker.com not only facilitated the drawing but also provided an online report, which the school shared via a link on their website. This allowed all participants to see that they were included in the drawing and that their weights were correctly applied.

The weighted lottery was a resounding success. It was praised for its fairness and transparency, ensuring that every student’s hard work and dedication were taken into account. The excitement among students was palpable, and the winners are eagerly anticipating their upcoming adventures abroad.