human eval

Averaging two scalar scores tells you almost nothing. Blind pairwise battles plus a win-rate confidence interval do, and the result is only trustworthy once you've controlled position bias, verbosity bias, and rater fatigue.

There's no single number. The trap is reaching for perplexity or BLEU because they're easy to compute, then optimizing a score that has nothing to do with whether the output is good. The move is to match the metric to the task and name where each one lies to you.