Stat Question

[backwardsk]

This has bugged me for awhile. Why is K:9 referenced instead of K:PA? Wouldn't the latter better capture a pitcher's ability to strike someone out?

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[Why Not?]

Per 9 innings is an easy context to understand. That's why it's used for ERA and similar stats.

K:PA would absolutely be more exact, but the number would not immediately register with fans.

[DrungoHazewood]

As Why Not? said, a metric can only effectively tell a story if it's both accurate and understandable. OPS isn't as accurate as some other offensive numbers, but it's close and almost everyone has a frame of reference for what's good and what's not. Everyone understands that nine K/9 is good, five is not so good, and 12 or 13 is excellent. What's the scale on K/PA? If someone tells you Chris Sale is striking out batters in 23.9% of PAs is that great? Terrible? Would you know that he's down from over 30% last year?