How do I calculate a weighted average based on two factors? I have seen a couple questions relating to this on this site, but none that are quite right.
Say I am trying to calculate the average number of bananas that are found rotten per day per bushel of bananas. I have the following measurements:
rotten bananas days bushels rotten bananas/(day*bushel)
3 2.2 5 0.27
5 2.3 2 1.09
1 1.8 3 0.19
etc.
I understand how to do a weighted average of rotten bananas/day and a weighted average of rotten bananas/bushel, but can't figure out how to combine the factors.
Does a weighted average even make sense for this sort of statistic? Especially if, say, these measurements were taken at 3 different stores over the same weekend. Would a better indication of the "average" rotten bananas per day per bushel be a normalized number of rotten bananas over 2 days. For example:
rotten bananas days bushels rotten bananas/(day*bushel)
2.73 2 5 0.27
4.35 2 2 1.09
1.11 2 3 0.19
So that's ~8.19 rotten bananas in a 2 day period in a total of 10 bushels. So would an overall "average" of something around 0.41 rotten bananas/(day*bushel) make some sort of sense?
Best Answer
Following my Comment, I get $$\frac{0.27(11.0) + 1.09(4.6) + 0.19(5.4)}{11.0+4.6+5.4}.$$ Please see if you agree with my logic and check my math.