# The Spectre of Math

## November 11, 2008

### Ebay math

Filed under: Mathematics — jlebl @ 4:11 pm

Somebody should be smacked upside the head. I am not a big ebayer, but sometimes I buy a few things there. Hence I do not have too many “ratings.” Now recently I looked into their page “how are these ratings calculated” because it says my positive feedback rating was 0%. Now this is because I had no ratings in the past 12 months. So far so good, though it does seem arbitrary to then make it 0%, it could have been 100% or any other number just as well.

Now comes the fun part. So they give a formula on how to compute the percentage: $\frac{Positive}{Positive + Negative}$. Allright, so far so good, except I had no ratings. Next they give their calculation and write:

$\frac{0}{0+0} = 0\%$

Hmmm … now I know why the ebay interface is so horrible, it is designed by people who think $\frac{0}{0} = 0$.