Measuring Performance with Plus-Minus

Measuring performance in a raid is somewhat hard. You can do a bit with damage and healing meters, but those meters are often skewed by the specific fight or class or spec. Sometimes it's hard to track the small things, like people who hit cooldowns at the perfect time, or kite mobs perfectly, or step beyond their specific role at the absolute correct time.

There is a statistic in ice hockey called Plus-Minus. If you're on the ice when your team scores an even-strength goal, you get +1. If you're on the ice when the opposing teams scores, you get a -1. So at the end, if you're positive, it implies that you are helping your team. If you are very negative, your presence on the ice actually hurts the team.

Of course, it's not a perfect stat. Since it relies on the team, a person on a bad team usually has a lower plus-minus than a person on a good team.

But it might be an interesting stat to use to measure a player's contribution to her raid team. After all, the ultimate goal is killing bosses. If you being in the raid means that bosses are more likely to be killed, then you are doing well. If the raid is more likely to wipe if you are in raid, then that's a problem. Rather than trying to measure and quantify the individual aspects of your role, we could just try and measure your effectiveness.

Here's how I'd set up a Plus-Minus system for a Raid Guild:

1. +1 for each boss kill.
2. -1 for each boss wipe.
3. Only count a maximum of 4 wipes per boss. This is so that raids with an obviously bad composition don't just give up to keep from wrecking their rating.
4. Don't count wipes on new bosses that haven't been defeated.

Going by this system, I was +4 this week. Not bad, but not really good either. But Plus-Minus is a relative system. So it would depend on what scores my other guildies would have.

Of course there are issues with this system. People who are in the raid all the time will have the same rating. It's not a problem in hockey because people are constantly taking shifts out on the ice. Certain bosses are more likely to cause wipes than other bosses. The method only works if you actually expect there to be some wipes.

Ultimately, killing bosses is the goal. Measuring effectives by how much a raider contributes to that goal might be a better method than trying to rank damage meters. But on the other hand, going through meters gives feedback on how to improve. A Plus-Minus system only identifies outlying players in either direction. It does not say how that player makes the raid better or worse.