When scouting individual players on the field, it's important for the scouting community to have a consistent list of attributes that relate to professional success. In addition, utilizing the same rating scale is important to assist player evaluation personnel when comparing different players. This post will look at the 20-80 evaluation scale that professional scouts use for player evaluation.
The 20-80 Scale
Some organizations use 2-8 rather than 20-80, but the purpose is the same: 50 is MLB average and every ranking below or above 50 is one standard deviation below or above the MLB average for that attribute. A player receiving a 70 rank for arm strength is thought to be 2 standard deviations above average, making the scale probabilistic in nature: That players arm is, in the scout's opinion, in the top 3% of all arms he's ever seen in his time evaluating players.
Keep in mind that less than 1% of all players a scout sees will ever see an inning in a professional uniform, much less Major League Baseball, so the top 3% of arms isn't nearly as limiting a factor as it sounds. An 80 on the scale would be extremely rare, an attribute that only 1 or 2 players in a population of 1000 would possess.
Some scouts will also give two rankings for each player scouting category (Ex. Arm: 40/60; Hit 50/60). The first is the rating for the players current level of ability. The second is a projection, based on years of experience, about what that player's level of ability could be after a few years of professional coaching and instruction. That's the scout's professional opinion on whether the player can improve his tools (raw ability) into valuable baseball skills (refined ability).
Next time: Defining the tools and skills that professional scouts use for evaluation.