Ok I might be asking something stupid, please bear with me, math is not my strong suit. This has to be a duplicate but I dont know how to search them. I dont even know how to word the title, kindly help me there too.
Question
I was trying to find the average win-loss record of a player over a period of 4 years. His win-loss record looks like:
19/23, 13/16, 21/24, 19/22
which means in the first year he won 19 of his 23 matches, in the second year he won 13 matches and lost 3, in the third year he played 24 times and won 21 times, and so on.
I want to find his consistency and hence I am looking for his average winning rate over the 4 years.
I thought it was quite straightforward but quite surprisingly it occurred to me that I can go about it in two ways when I found some discrepancies in the way I calculated it:
Add up all the wins during the 4 year stint and divide by the number of total matches played during that time.
So my player's consistency is measured like
(19 + 13 + 21 + 19) / (23 + 16 + 24 + 22)
which is 84.7%
Finding the average of win percentage of the 4 samples.
So my player's consistency is measured like
(19/23 + 13/16 + 21/24 + 19/22) / 4
which is 84.43%
Well at first being so naive I thought either way I should get the exact same result, but no! I then thought there must be some rounding issues in the second case which is why I get a different but close number. I tried to form a theoretical basis like shown below.
Let's say a player won "a" matches out of "b" matches played in first year, and in second year he won "c" matches out of "d" matches played. His consistency can be measured by the above two models like:
(a + c) / (b + d)
or
(a/b + c/d) / 2 => (ad + bc) / 2bd
Clearly the two aren't the same. So my questions are:
a. What is the practical difference between the two ways to calculate consistency? I'm not asking for a strict mathematical definitions, but trying to know in what real world scenarios the two different approaches make sense? The nature of my question is similar to this question. I want to know how to calculate a player's consistency over a period of time and which model fits where.
b. Are there any technical terms in math world to denote the two ways of assessing average?