I am currently coding a script which displays data for a company intranet. I am stuck with a question that seemed pretty simple, but turned out to give me headaches.
We have the following scenario:
Store A has 70 male customers and 100 female customers - (170 total) Store B has 50 male customers and 230 female customers - (280 total)
Now, I learned that in order to display the average male/female ratio I have to calculate:
(male store A + male store B) / (170 + 280) = X
X * 100 = 28.9% males / 71.1% females
Yet when thinking it over, it doesn't show the real average, because the total number of clients isn't the same (170 vs 280).
So I did a second approach, which is first separating the percentage by store, and then calculating the average percentage:
Males, Store A: (70 / 170) * 100 = 41.2% Males, Store B: (50 / 280) * 100 = 17.9%
And then divide it:
(41.2 + 17.9) / 2 = 29.6%
So in the second case, rounded up, male ratio is 29,6% instead of 27,3%
Then I showed both calculations to somebody who is better in math then me, and he told me that both are wrong. He said I should use "weighted average", but when I do i get exactly the same average percentage like in the first calculation.
What am I doing wrong?
Background: We have a lot of stores, each with a different number of female and male clients. I want to have a percentage of the average client gender, but taking into account the different amount of the guests in each store.