This article is part of our The Saber's Edge series.
I chose Steamer's historic projections as a test group. One data anomaly I found immediately was that the projected number of plate appearances ran a little high; I talked to the creator of Steamer, Jared Cross, who said he wasn't aware of the issue but will look into it.
Even with the small bias, Steamer is considered the most accurate projection system and is always upgrading, such as using pitch velocity as an input. It's a perfect projection system for today's study.
The Steamer projections go back to 2010, and the plate-appearance numbers are derived from FanGraphs fan playing time estimates and depth charts.
To start, here are the plate-appearance distributions compared to the actual results by percentiles.
|651 to 700||Projected||689||680||666||656||652||183|
|601 to 650||Projected||647||637||625||614||606||340|