Filling a water bottle at a public fountain is a pain. It never fits, so you have to flip your bottle aside – which makes it even more difficult to get the water in your tight mouth. However, there are new devices that solve this problem. Maybe you saw her in office buildings or at airports. In addition to a normal drinking beak, there is a special outlet only for bottles.
Well, here's the thing. At my university, they recently upgraded our old hall fountain in this new way. Cool, right? This special model has a digital counter at the top labeled "Save bottles". What? Do you know what this means? This means that I can track the counter value over a longer period of time and see what happens.
I am honest. I really can't help myself in such cases. I just love collecting data. I don't even know what I'm looking for. Just browsing.
Source of Truth
Okay, let's start with the numbers. I usually checked the meter reading at least a few times a day for several months. So here is a graphical representation of the counter value as a function of time. The time units are in days, but I converted the approximate hour to a fraction of a day.
So what do you see here? These are my first observations:
- It is fairly linear. If it were completely linear, people would go by and drink at regular intervals. Of course, people are never that predictable.
- Sure, I didn't collect a lot of data on the weekends, so there are some blank areas. There's a longer gap around day 40 ̵
- Nevertheless, it seems that there is not much use of the well on weekends. The values for Friday afternoon and Monday morning are pretty similar.
- After about 60 days, the line becomes flatter. This happened after final exams.
So let's make a rough estimate of the usage rate in "number per day". This would be the slope of the data above. If I only adjust the data as it is (including minor weekend use but deletion of vacation data points), I get an average bottle count rate of 22.29 per day. If that's really the number of disposable bottles saved per day, that's pretty good.