Decided in advance. Not by a click.
Fair random scheduling
The whole point of a random schedule is that nobody in the agreement chooses the day. Here's how P in the Cup is designed to make that true, in plain language.
The app is launching soon
The app is still in development. This page explains the principles the schedule is built on. The exact rules for edge cases are being finalised, and we'll update this page before launch.
Step by step
How a schedule is drawn
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You agree on a frequency
Participants agree on how often a test day should come up, such as about once a week, and on the period the agreement covers. This is the only part anyone chooses.
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The server draws the days
The app's server, not anyone's phone or browser, uses a random number generator to decide which days are scheduled, following the agreed frequency.
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Each day is settled before it begins
A day's status is fixed and stored before that day starts. When you check "Is today the day?", the app reads that stored answer. It doesn't generate a new one.
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You find out on the day
Participants learn each day's status on that day, so the schedule can't be planned around.
Why it matters
Why the day is decided before it begins
If checking the app made the decision, a "Scheduled day" answer could be dodged by checking again, or blamed on whoever pressed the button. Deciding in advance removes both problems.
No rerolls
Refreshing the page, closing the app or checking from another device shows the same answer, because the answer already exists.
No one to blame
Nobody in the agreement picked the day, so there's nothing to argue about. "The schedule chose it" is the whole answer.
No timing games
Because the answer was fixed ahead of time, the moment you choose to check can't change it.
Fairness in plain language
What "fair" means here
A fair schedule has two properties:
- Every eligible day gets a fair chance under the agreed rules. No day is quietly favoured or skipped beyond what the agreed rules say.
- No one in the agreement picks the day. Not the person being tested, not a partner, not a group organiser.
Computers generate random choices with a random number generator. Many generators are pseudo-random: they produce numbers from a starting value called a seed. A generator designed for security, seeded with unpredictable data and run on a server that participants can't access, produces choices that nobody can practically predict or steer. P in the Cup draws its schedules server-side for exactly this reason: the choice happens somewhere none of the participants control.
We won't publish claims about a specific algorithm or an independent audit until they exist. When the app launches, this page will describe the method actually in use.
A common surprise
Why "random" doesn't mean "evenly spaced"
People often expect a random schedule to look tidy: one day a week, spread out neatly. Real randomness doesn't work that way, and that's what makes it unpredictable.
- Two scheduled days can land back to back.
- A long stretch can pass with no scheduled day at all.
- Some weeks will have more scheduled days than average, and some fewer.
If the schedule were evenly spaced, anyone could work out the next day after seeing a few. Clusters and gaps are a sign the schedule is doing its job, not that something is broken.
An illustrative example Example
Imagine a rule where every day independently has a 1-in-7 chance of being scheduled, about once a week on average. Over a four-week stretch the average is 4 scheduled days. But by the arithmetic of chance alone, about 1 in 5 such stretches would have 2 or fewer scheduled days, and about 1 in 5 would have 6 or more. This is a worked maths example, not a description of the app's exact rule, which is still being finalised.
Real life happens
Edge cases
How these are handled depends on what the participants agree and on the app's rules, which are being finalised. Talk about them before you start, not on the day.
A missed day
What a missed scheduled day means, and what happens next, is up to the people in the agreement. Deciding this in advance keeps it a matter of the rules rather than an argument.
Travel and time away
Being away from home or your kits can make a scheduled day hard to complete. Agree beforehand how you'll handle it, for example by taking a kit with you or agreeing an alternative.
Changing the agreement
Agreements can change as circumstances change. Any change should be agreed by everyone involved. Whether and how a change affects days already drawn will follow the app's rules, confirmed before launch.
Cost
The random scheduling and accountability service is free. Test kits and any laboratory testing are purchased separately.
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