Statistical Explanations
Here you can find explanations of those hard-to-understand stats and reports in Nostalgia Baseball.
Player Impact
The player impact report contains valuable information about each player's impact on your team's won-loss record and ability to prevent/score runs. It's unwise to rely too heavily on any diagnostic tool. But this report can help you assess the value of each player's overall contribution because it integrates defense, offense and pitching. It's not very helpful for comparing your players with players on other teams, however. Like any data, you must develop the skill of interpretation by understanding what is and is not being measured and remembering that reliability increases with the amount of raw data compiled.
Won-Loss Record
The report shows your team's won-loss record when individual players appear in the starting lineup. Unlike most reports, this one includes only the player's productivity on your team, so if you got a player in a trade don't expect to see cumulative numbers.
Plus-Minus Scores
Here's a description of what the numbers mean in each column:
+/- Runs
Every time your opponent scores a run the computer tallies -1 for each player currently on the field. Conversely, every time your team scores a run the computer tallies +1 for each player in your current lineup, except for pinch hitters and designated hitters. Since pinch hitters and designated hitters could never receive a minus tally, their scores would be unfairly inflated. So, we leave these appearances out.
+/- per Game
In this column you'll notice that the +/- runs are adjusted to reflect a ratio for each game (9 innings) played. This evens out the discrepancies in playing time between your players so that you can compare them against one another.
+/- Deviation from Team
In this column you'll see (on a per game basis) player x's deviation from your team's average with player x's stats removed. A negative number indicates that the player is less effective than the average player on your team. A positive number means the player is more effective that the average player on your team. Because pitchers can so dramatically effect outcomes, their scores usually deviate the most, which in turn impacts everyone else's score. If you have an overpowering pitching staff, chances are most of your offensive players will show as negative. It doesn't mean they're necessarily ineffective, just that in comparison to your team's overall ability to score/prevent runs they fall below the mean. If your pitchers are lousy as a bunch, your offensive players will appear mostly as positive.
Plus-minus scores are a handy way to get a handle on some things that otherwise might be hard to detect, like how important a particular catcher's defensive ability might be to your team even if he doesn't hit so well, or whether a catcher can produce enough offensively to outweigh a weak arm, or whether it's wise to think about a platoon combination at a position, or how starting pitchers might effect the overall chances of you winning a game even when they get a no-decision, and so on.