Bases Batted in 2015 MLB

As a follow-up to a previous post, I sat down to compute the number of bases generated by MLB player at bats as documented in the 2015 play-by-play data from Retrosheet.org.  Due to data limitations, the National League was neglected, though the error margins suggest that we're dealing with a large enough sample with the American League to serve as reasonable estimates for all MLB.

Here's are the aggregate stats detailing the frequency and probability of base-runner distribution, stratified by the base-runner positions:

2015 - AL	None	R@1st	R@2nd	R@3rd	R@1,2	R@1,3	R@2,3	R@1,2,3
Frequency	48498	15041	6234	2007	5403	2271	1509	1756
Probability	58.6%	18.2%	7.5%	2.4%	6.5%	2.7%	1.8%	2.1%
Margin of Error	0.4%	0.6%	0.7%	0.7%	0.7%	0.7%	0.7%	0.7%

Runner movements after each at-bat with runners on base were also tabulated, which are included merely for the purpose of making these results reproducible/verifiable:

FROM 1ST	R@1st	R@2nd	R@1,3	R@1,2,3
Runner lost	2560	765	372	232
No Advance	7623	2993	1142	893
Batted to 2nd	2704	924	421	367
Batted to 3rd	1269	392	199	157
Batted Home	835	312	122	94
Hm - unearned	50	17	13	13
Hm - unearned team	0	0	2	0
FROM 2ND	R@2nd	R@1,2	R@2,3	R@1,2,3
Retired Side	134	176	22	34
Runner lost	3843	3182	976	1016
Batted to 3rd	1184	1011	243	327
Batted Home	992	944	238	341
Hm - unearned	79	89	29	36
Hm - unearned team	2	1	1	2
FROM 3RD	R@3rd	R@1,3	R@2,3	R@1,2,3
Retired Side	36	56	39	79
Runner lost	1307	1383	938	1015
Batted Home	608	737	474	591
Hm - unearned	56	94	57	71
Hm - unearned team	0	1	1	0

After excluding unearned advancement home, all remaining base advancements were given a positive weight of 1, with the appropriate negative weight applied for runners lost from 1st, 2nd, and 3rd respectively (-1, -2, -3) due to a force-out, tag-out, or when the side was retired.  In this way, the total bases gained/lost after each of these at bats was tabulated under each runner condition:

2015 - AL	R@1st	R@2nd	R@3rd	R@1,2	R@1,3	R@2,3	R@1,2,3
Frequency	15041	6234	2007	5403	2271	1509	1756
Total Bases	5187	2900	500	4426	1382	1032	2026
E(bases)	0.34	0.47	0.25	0.82	0.61	0.68	1.15
Margin of Error	0.017	0.021	0.028	0.018	0.026	0.028	0.025

Using these averages as approximations for the expected bases from each condition, we can might compare the results of a batted bases of an individual player to that of the league average, but that seems like a matter of another post.