## Saturday, May 10, 2014

### How Is Vegas Doing On Park Factors?

Below is a table showing each teams actual park factor (runs) and the Vegas park factor which is calculated by reverse engineering their over/unders for each game and using that as a proxy for actual runs scored for each game. The table is sorted by which actual park factor is closest to the Vegas park factor. The teams at the top of the list are playing in a run environment at home close to where the betting public is predicting it to be. The teams at the bottom of the list are having a lot of random variation when it comes to their home park run environment so far in this young season. Small sample sizes and regression to the mean are at play here but it is interesting to see how things are shaping up so far with the empirical data.

TeamActual PFVegas PFDelta
Dodgers0.9920.9980.005
Reds1.1181.0820.036
Twins0.9410.9780.037
Mets0.7910.8470.056
Rangers1.0091.0650.056
DBacks1.0131.0710.058
Braves0.9220.9810.059
White Sox1.0350.9620.073
Phillies0.8270.9100.083
Marlins1.1361.0340.103
Giants0.8490.9510.103
A's0.7830.8880.106
Indians0.9071.0140.106
Blue Jays1.2191.1030.116
Tigers0.9301.0600.130
Pirates1.0470.9120.136
Rockies1.4731.3210.152
Yankees0.8721.0370.165
Cubs1.1670.9930.174
Mariners0.7380.9310.192
Rays1.1230.9270.195
Nats0.7730.9880.215
Red Sox1.2481.0210.227
Royals1.2851.0520.233
Astros1.2611.0200.241
Angels1.2530.9640.288
Orioles0.6941.0170.324
Brewers0.6671.0560.388
Cardinals1.3750.9740.402

MP said...

Just curious: how did you calculate the actual park factors?

Xeifrank said...

Actual park factors were calculated the simple way.

(Home RS + Home RA)
divided by
(Away RS + Away RA)

The exercise was to compare empirical data vs Vegas data.