Decision making website app / site with hidden preferences

September 17, 2021 12:13 PM

When 2 or more people are faced with an unimportant or fun decision, I would love a thing where we can each enter in our preference for it, hidden from the other, and the oracle on the computer end tells us what to do based on the averaged preferences. Example: "Should we go to that party tonight?", on a scale of 1-5, X enters 2, the app hides their entry, X hands the phone to Y, Y says 1, gives it to Z, who says 4, but since the average was under 3, the computer says no without explicitly revealing the numbers or who entered them, and we're free. I feel this must exist but I'm having trouble finding one. Can be an app, site, a way to do this with a piece of paper, whatever. Any ideas?

(I assume we'd have to set the default action for a equally divided result beforehand, and of course in my example Z would know X or Y were more no than them, but they wouldn't know precisely which or how much. I'm not planning to use this for anything too important or personal where privacy is a big risk.)

posted by neustile to Computers & Internet (9 answers total)

It wouldn't be hard to write such a thing. (Mefi jobs?) A no-programming version would be to make a Google Forms survey with one question on a five point scale, then edit the spreadsheet to hide columns A and B and, add the line "=AVERAGE(B1:B1000)" to column C, and bookmark the spreadsheet. Maybe make ten of them ahead of time. (The person who controls the form could always cheat and see the ordered votes, but if you trust them not to do so, it's really easy to implement.)

Colored jellybeans and an opaque jar is another version. It means planning ahead. But you do get to eat jellybeans.
posted by eotvos at 12:50 PM on September 17, 2021 [1 favorite]

Best answer: If any one of you has an iPhone I could whip up a Siri shortcut that does this. In fact now I want to. Ok I did it. (I'm procrastinating) You can download it from this link: link
posted by bleep at 12:55 PM on September 17, 2021 [30 favorites]

Response by poster: For the colored jellybeans, wouldn't that require a non-involved third party to count them so that no one else knows what they were? Unless I'm misunderstanding
posted by neustile at 12:56 PM on September 17, 2021

Response by poster: OMG. bleep! I just installed it and it's perfect! It's so cool it can work on voice or typing in (more discreet.) I had no idea Shortcuts got so useful. And I can just ask Siri for "group decision"! <3 (I'm going to modify a copy so it just says "yes" or "no" instead of showing the average, which I assume could leak the makeup of the input numbers.)
posted by neustile at 1:00 PM on September 17, 2021 [3 favorites]

(Oh yeah sorry about that, I just had it there for testing but the one at the download link doesn't have that anymore)
posted by bleep at 1:08 PM on September 17, 2021 [2 favorites]

A simple way to do this without a phone would be to give everyone (n people) two items (pebbles, slips of paper etc) and have everyone either drop one (no) or two (yes) into a container. If the total number of items is greater than 1.5n that means at least half vote yes.

So for example, 6 people, you distribute 12 items, when you check the count there are 9 inside - means you go. 8 means a tie (coin flip?) and 7 is no. I just made this up so maybe there's a flaw here but hey, just in case bleep's script doesn't load...
posted by BlackLeotardFront at 6:03 PM on September 17, 2021 [2 favorites]

How about jelly beans of one color?
Each person can put them inside the opaque jar and everyone can count and see if it hits the threshold for “yes”
posted by calgirl at 7:41 PM on September 17, 2021 [1 favorite]

(In cryptography, this would be an example of the class of problems the subfield of secure multi-party computation addresses: everyone involved provides their own input and after the joint computation they only learn the result, and still know their own input, but nothing else.)
posted by meijusa at 4:30 AM on September 18, 2021 [2 favorites]

Metafilter: I could whip up a Siri shortcut that does this. In fact now I want to. Ok I did it.

Nerd sniping at its best.
posted by automatronic at 4:58 AM on September 18, 2021 [5 favorites]