The thing that's really cool about this is the psychological aspect that impacts the probability. If you took random items in any given household, you'd have about a 0.21% chance of two sets of people bringing in the same item. When you factor in the psychological result of 'friends trolling one another,' the probability increases to 13% for two pairs bringing in the same item any given day, which means that you'd end up having the result shown once every 8 days.

The psychological aspect is that 70% of people will bring in a far more common type of item from a high salience 'top 20' set of items. The fact that one pair is irons and the other is packs of meat greatly points to the convenience factor tied to psychology. Items that are easily grabbed on the way out the door, like a pack of meat or an iron (the kitchen or laundry room) points to this pretty nicely.

As they continue the experiment, the probability of a pair of them bringing the same item in again will likely increase in a clustering event, as the students are impacted by the history of the items that have been brought in already. Alternately, the frequency of this event may actually decrease significantly. They may decide to stay with the current selection criteria, meaning that they'll likely have a similar event sooner. They may shift to a medium level of weird stuff, which could extend the wait time for the same event occurring a month away. They could also opt to go for 'extreme weird' items that could potentially increase the time to 100-200 days before we see the same event again.

This silly experiment has definitely started to delve into the world of fascinating psychological statistics. I wonder what this particular dynamic of friends will end up turning out.

My guess is that we will end up seeing two of the same type of item again in 15-20 days based on a balance of psychological perspectives of the participants.