Who Would Be the Tea Sponsor for Today? — आज कसको चिया खुवाउने पालो हो?
By: Suraj Regmi
Tags: Tea, Diary, Math, Probability

InfoDevelopers, the first organization I worked professionally and the company that nurtured me from a fledgling into a professional, had a great culture of Tea Sponsorship in occasions. A colleague sponsors tea for whole the department on his/her occasion and the occasion gets celebrated with the sip of tea and cheers. Such culture, which I believe was brought by Ismaran Duwadi in our block, not only provided fun but also strengthened the relationship between colleagues.

In AI/Python department, at some point of time, there were eleven people, with me included. We had planned to make an order in which tea sponsorship was to be made daily as the occasions started to become rare. Once the order is complete, the order can either be reset or can be continued cyclically. As the first employee of the department and one of the senior members of the team, I took some part of leadership in bringing fun to the team and sharing knowledge. I had always something to share on mathematics, programming and artificial intelligence to the team.

Coding was fun. Solving problems was delighting. Teamwork was excellent. Management was understanding. Above everything, one thing there refreshed me each and every day. It was just an inquiry someone made everyday.

आज कसको चिया खुवाउने पालो हो?

English translation: Who would be the tea sponsor for today?

When I reflect on the journey of InfoDevelopers, such small things make me smile. With the smile the memory has mirrored, I am wondering about the order of the tea sponsorship. No one wanted to be first in the order nevertheless everyone had to go through the order only once. I also did not want to be first in the order. Human behavior!

The order selection is done randomly. Suppose I make my favorable order and bet at least one of the person is positioned as per my favorable order. If I do such bet with my colleagues, is my bet foolish? I came to think this thing.

If I had done such bet, I would not be foolish. I worked the mathematics of probability and found that it is 63.21% probable that I would win. In 100 bets I make, I am highly likely to win around 63 bets. However counter-intuitive it seems, it is mathematically true. Period!

To see validity of this statement, we should work through inclusion-exclusion principle of probability and apply it to our problem. It is actually a case of Montmort’s Problem. Readers interested in its mathematics are strongly advised to go through the link. The probability that my bet wins in the group of n people is given by:

Probability = 1 — (!n)/(n!),

where !n is subfactorial of n or number of derangements of a set with n elements.

We can calculate the probability with the below Python one-liner once you enter the value of n.

Run the Python code, enter the value of n as 11 and the probability would be printed as 0.6321.

सजित: आज कसको चिया खुवाउने पालो हो?

राजन: अरुण भाइको होला आज त!

गौरव: मलाई चाहिँ कोल्ड लेमोन है।

दकिंग: आज भाइले मलाई कोल्ड कफी खुवाउछ :P

अरुण: दाईले भने पछि कसरी नाइँ भनु म :D

सुरज: मलाई नि कोल्ड लेमोन नै हो कि अरुण?

रुपेश: मलाई जे भए नि हुन्छ केटाहो!

विशाल: (मुस्कुराउदै) गर न कोल्ड लेमोन मलाई नि।

नितेश: लेखम न त कसलाई केके चाहिने हो।

दिपेश: म त सधै कोल्ड लेमोन हो है।चिया खान हुन्न मैले … (खुलेर हास्छ)

संदेश: (गौरवतिर फर्कदै) जिग्री, तिमी के हो, चिया कि कोल्ड लेमोन?