What measure describes the relation between time taken vs. errors in the result?

I'm evaluating an algorithm's performance. The more time the algorithm runs, the less errors in the result.

I'm taking multiple measures of this (time taken vs. number of errors) to explain the trade-off between time taken and errors in the result. Does this measure have a name? I'm sure I'm not inventing anything new, but I've been unable to find it by myself.