One of the most misleading of all the sabermetric devises is the use of probabilities that a run will score or a team will win as a measure of individual results.
The basic idea, made popular by a guy with the nom-de-plume of Tango Tiger, is how many runs to teams score a run or games do they win after a change on the field.
As an example. how many runs do teams score with one out and runner on first, compared to one out and a runner on second. How does that compare to to two outs and no one on base. This is used to determine the value of a stolen base, compared to getting caught stealing. You can see a recent example of this methodology here: http://www.twinkietown.com/2011/3/29/2078456/baserunning-was-it-really-a-problem-last-year .
You can take this a step further and ask - what is the impact on wins. For instance, You start with how often teams win with a score of 3-2 in the bottom of the 8th with no one out and no one on base. After a player doubles, you compare that to how often a team wins in the new situation, with the score still 3-2 in the bottom of the 8th with no outs, but now a runner is on second.
At first glance this seems like a reasonable measure. But it is no more reasonable than it is to say "How often do players hit home runs?" and then apply the result to Justin Morneau and Matt Tolbert. While the number of outs and runners on base are certainly factors in how often a team will score, who those runners are, who is pitching, who is in the bullpen, who is batting next .... are all at least as important. So when you make a decision to bunt or steal, you have a lot more to consider than what will happen on average in the new situation.
The fact is that baseball results are not random data. They are being influenced constantly by players and managers on both teams acting to optimize the results in their favor. Players don't randomly steal bases based on the number of outs. Managers don't randomly bunt. In fact, players don't even approach each at bat randomly and neither do pitchers. Its only through willful ignorance, ignoring what players, managers and professionals tell us about what they are doing, that we can pretend that this kind of analysis gives us any real insight.