Deciding Dinner for a Group of Eight
Dietary constraints shrink the pool before any draw, and someone always forgets to mention one.
At eight people the dietary and budget constraints usually cut the option list to three or fewer before anything is drawn, so the entire difficulty has moved into collecting constraints from people who did not mention them.
At eight people the constraints usually cut the option list to three or fewer before anything is drawn. The difficulty has moved entirely into collecting constraints from people who did not mention them.
That is the actual work, and no draw improves it.
Collect the constraints before you propose anything
Ask once, in a single message, for everything that would rule an option out: dietary requirements, allergies, things people cannot eat for other reasons, budget ceilings, and how far anyone is willing to travel. Ask before you have suggested anything, because a constraint mentioned after a suggestion reads as an objection to the suggestion.
The commonest failure is a constraint that arrives late because the person did not think it applied. Someone who does not eat shellfish will not mention it in response to "where shall we eat" and will mention it in response to a specific restaurant, at which point you are back to the start with a suggestion already rejected.
A single explicit request produces a much more complete list, and it produces it before anyone has anything to react to.
- Ask in one message, before proposing anything.
- Ask specifically: diet, allergies, budget ceiling, travel limit.
- Expect at least one late constraint anyway, and plan the timing around it.
- Collect the constraints privately; some of them are nobody else's business.
What eight people does to the option pool
Each additional person adds constraints roughly independently, and their effect on the pool multiplies. If each person rules out about a fifth of the options, eight people leave roughly seventeen percent of the pool — and if each rules out a third, eight people leave under four percent.
That is why a group of eight so often ends up at the same three places. It is not a failure of imagination; it is what an intersection does, and the three surviving options are genuinely the intersection.
The dinner decider shows the surviving count for exactly this reason. Watching the number fall as you add filters makes the arithmetic visible, and a group that can see there are three options left argues about them differently.
How the pool collapses
- Each person rules out 20% of options: 8 people leave about 17% of the pool.
- Each rules out 33%: 8 people leave under 4%.
- A group of eight ending up at the same three places is arithmetic, not habit.
Where the draw actually helps
Once the pool is down to three or four genuinely viable options, the draw does something the group cannot: it produces an answer nobody proposed. That matters more at eight people than at two, because at eight the person who proposes something has effectively spent social capital and will defend it.
It also matters because the loudest preference otherwise wins by default. In a group of eight, one person stating a strong preference first will usually settle it, and a draw over the viable options removes that path without anyone having to object to it.
So the honest summary is that the constraints do ninety percent of the work and the draw does the last ten. The last ten is still worth having, because it is the part where groups get stuck.
Booking, which is the real constraint
For eight people the binding constraint is usually availability rather than preference. A table for eight on a Friday needs booking, and the options that survive your dietary and budget filters may not survive the availability one.
The practical order is therefore: filter, draw, check availability, and if the drawn option is unavailable, draw again from what remains. Re-drawing for availability is legitimate in a way that re-drawing because you did not like the answer is not, and the difference is worth stating out loud to the group.
Checking availability for all three surviving options before drawing is better still, and it takes about five minutes.
Frequently asked questions
Why does the option list collapse so fast at eight people?
Because constraints multiply. If each person rules out a fifth of the options, eight people leave about seventeen percent of the pool.
When should I ask for dietary requirements?
In one message, before proposing anything. A constraint mentioned after a suggestion reads as an objection to the suggestion.
Why do people mention constraints late?
Because they do not think it applies until they see a specific option. Asking explicitly and in advance produces a much more complete list.
What does the draw actually add?
An answer nobody proposed, which matters at eight people because the proposer defends their suggestion and the loudest preference otherwise wins.
Is it legitimate to redraw?
For availability, yes — say so out loud. For not liking the answer, no, and the difference is worth stating to the group.
Should I check availability before or after drawing?
Before, for all the surviving options. It takes about five minutes and removes the commonest reason for a redraw.
What if only one option survives?
Then you have your answer and there is nothing to draw. That is a normal outcome for a group of eight.
Should constraints be collected privately?
Where possible, yes. Some dietary requirements have reasons that are nobody else's business.
Tools for this job
Background reading
Constraint Satisfaction in Fair Draws
What happens when the rules and the randomness disagree — and when there is no answer.
How Weighted Random Selection Works
Cumulative sums, one float, and why duplicating entries is the wrong way to do it.
The Law of Large Numbers, Practically
What 'it evens out' actually promises, on what timescale, and what it never promises.