The results in the last column are what we would expect if the four factors--batting, baserunning, fielding, and pitching--were appropriately weighted in the calculation of bWAR.
Baseball-Reference's treatment of pitching vis-a-vis fielding makes it difficult to evaluate the accuracy of bWAR as compared to fWAR or eWOPA.
In that case, the test of the hypothesis that the coefficient is equal to zero may lead to a failure to reject a false null hypothesis of no effect of the explanator, a type II error." In layman's terms, the standard errors associated with [a.sub.f0] and [a.sub.p0] are artificially large, because of the way in which Baseball-Reference calculates bWAR.
This should make bWAR a more accurate measure of actual team performance than either eWOPA or fWAR, neither of which tie their defensive measures directly to actual runs allowed at the team level.
This makes it very difficult to evaluate Baseball-Reference's treatment of fielding and pitching at the player level by looking at the team-level accuracy of bWAR (or bWAA).
As a final analysis, I compared bWAR to team WAR, where the latter was set equal to actual team wins minus the number of wins a .294 team would have won over that team's total games (47.6 per 162).
Having set all of that up, I fit the same equation as used earlier for eWins and bWAR, using Fangraphs data from 2003-15.
Table 11 repeats results presented earlier in this article that relate actual team wins to my eWOPA (eWins over positional average) and to WAR (Wins above Replacement), as calculated by Baseball-Reference (bWAR) and Fangraphs (fWAR).