※ [本文轉錄自 NY-Yankees 看板]
作者: leddy (耿秋) 看板: NY-Yankees
標題: Re: [統計] What is Zone Rating?
時間: Sun May 13 16:26:18 2007
※ 引述《leddy (耿秋)》之銘言：
: 因之前查Bobby Abreu的資料, 順道查到這篇好文Hardball Times的好文
: 來源http://www.hardballtimes.com/main/article/what-is-zone-rating/
: What is Zone Rating?
什麼是防守區域評價
: by Sean Smith
: April 02, 2007
: Zone rating has been around for 20 years now as a way to measure defensive
: players. It’s a simple concept; you just need to know two things: How many
: plays a fielder makes, and how many were hit into his zone. You divide the
: first number by the second, and you have zone rating. You can look at how
: many plays were made compared to an average fielder to get a plus minus
: rating, and that can easily be converted to runs to help us measure the
: overall worth of a ballplayer.
防守區域評價至今已經被用了大約二十年，是一種對防守球員評價的方法。這是一個
簡單的概念；你只需要知道兩件事；野手完成多少出局數；有多少球打進他的防守區域。
將第一個數除以第二個數，你就可得到防守區域評價的值。你可以看看這個野手完成多少
出局數與野手平均的出局數作比較，便可得到加或減的評價，這也可以很容易地轉換為得
分數，用來幫助我們對一個防守球員作整體評價。
: There’s More than one Zone Rating?
: Last winter John Dewan and Baseball Info Solutions published The Fielding
: Bible and introduced a new version of zone rating. Dewan happens to be the
: guy who came up with the old Zone Rating when he worked for STATS, and he was
: able to add an improvement in the treatment of plays fielded outside of the
: zone.
不只有一個防守區域評價值
去年冬天John Dewan和Baseball Info Solutions於野手聖經上發表的文章介紹新版
的防守區域評價的方法。Dewan恰好是為STATS工作時想出舊版防守區域評價值的人，所以
他運用了野手在防守區域外拿到的出局數，以改進舊版防守區域評價的不足。
: In the original Zone Rating, if a ball is hit outside of your zone but you
: range far enough to make a play anyway, that ball is added to both your plays
: made and your chances. The effect of this is to underrate players with
: outstanding range. Here’s an illustration:
: Take two shortstops, call them Billy and Jason. Both players have three
: ground balls hit near them, two in the shortstop zone and one just beyond it,
: hit straight up the middle. Jason makes plays on the two hit in his zone but
: cannot reach the other ball. Billy makes one play in his zone, makes an error
: on the other, but makes a great play on the ball hit up the middle.
: The zone rating for Jason is a perfect 2/2. For Billy, its 2/3, even though
: both players have had the same opportunities, and recorded the same number of
: outs. The new Zone rating treats these plays differently. Balls in zone
: counts only those hit into your zone, and there is a separate category for
: balls fielded outside your zone.
在原始的防守評價值中，假如球被打出你的防守區域，但是你的防守範圍夠大還是拿
到出局數(接到了球)，此球被同時加到你拿到的出局數和防守的機會中。這樣的結果低估
了一個有傑出防守範圍選手的價值。舉例來:
如果有兩個游擊手，就稱呼他們比利和傑森好了。這兩個防守球員有三個滾地球打到
接近他們的位置，兩個在游擊手防守的區域內，一個在防守的區域外直接打向中間而去。
傑森對打向防守區域內的兩球拿到了出局數，但防守區域外的球根本構不到球。比利則對
打向防守區域內球拿到一個出局數，另一個則發生失誤，但是打向中間跑出防守區域的球
卻用美技式的讓打者出局。以原始的防守區域評價而言，傑森是完美的2/2，但比利卻是
2/3，即使兩個防守球員有相同的防守機會，同時記錄相同數字的出局數。新的防守區域
評價則將這些出局數視為不同。防守區域內的球(Ball in zone)只計算打進你防守區域內
的球，而將用一個類別的值記錄落在你防守區域外的球。
: Let’s Check the 2006 Results:
: The new Zone Rating is now available on The Hardball Times website. THT has
: data for the 2004 to 2006 seasons, and will add 2007 data as soon as the
: games begin. To get a feel for how the new feature, balls out of zone,
: affects a player’s rating, let’s take a look at the shortstops for 2006,
: using the new data but calculated the same way as the old Zone Rating:
讓我們看看2006的記錄：
新的防守區域評價現在可以在The Hardball Times(THT) 的網站中查得到。THT有2004
至2006年球季的資料，而且將在球賽開始進行後儘快加入2007年的資料。來感覺一下新的
數字，防守區域外接捕的球(balls out of zone)，對一個防守球員評價值的影響。就看看
2006年游擊手的的數字，我們先用新的資料但用舊的防守區域評價的方法去計算：
: Name BIZ Plays ZR OOZ Chance Total Plays Above
: Plays AVG
: A. Everett 396 353 0.891 60 456 413 28
: O. Vizquel 352 306 0.869 36 388 342 14
: J. Reyes 359 308 0.858 40 399 348 11
: C. Barmes 315 269 0.854 51 366 320 11
: J. Bartlett 293 253 0.863 26 319 279 10
: A. Gonzalez 269 230 0.855 42 311 272 9
: E. Renteria 368 309 0.840 55 423 364 7
: D. Eckstein 320 269 0.841 43 363 312 5
: J. Uribe 333 280 0.841 40 373 320 5
: K. Greene 286 238 0.832 36 322 274 2
: R. Cedeno 322 265 0.823 54 376 319 1
: J. Rollins 413 342 0.828 46 459 388 0
: J. Wilson 401 330 0.823 48 449 378 -1
: M. Young 458 375 0.819 53 511 428 -3
: B. Hall 294 234 0.796 66 360 300 -4
: C. Guillen 406 330 0.813 49 455 379 -5
: R. Furcal 458 372 0.812 57 515 429 -6
: Y. Betancourt 399 322 0.807 55 454 377 -6
: M. Tejada 394 318 0.807 44 438 362 -8
: D. Jeter 385 310 0.805 28 413 338 -11
: H. Ramirez 368 290 0.788 61 429 351 -11
: A. Berroa 364 286 0.786 36 400 322 -16
: J. Peralta 459 364 0.793 46 505 410 -16
: O. Cabrera 351 273 0.778 44 395 317 -17
: Definitions:
: BIZ: Balls in zone
: Plays: Plays made in zone
: ZR: Zone rating
: OOZ: Plays made out of zone
: Chances: BIZ + OOZ
: Total Plays: Plays + OOZ
定義：
BIZ: 防守區域內的球
Plays:防守區域內拿到的出局數
ZR: 防守區域評價
OOZ: 防守區域外拿到的出局數
: Plays above average is found by finding the league average ZR, multiplying by
: Chances, and comparing to total plays made. This is for illustration
: purposes; I am using the total of this group of qualified players instead of
: the actual league average which would include starters and reserves. In
: addition, Chris Dial uses (correctly in my opinion) the AL and NL averages
: instead of an overall MLB average. There are factors (such as pitcher
: hitting) that make within league comparisons more accurate than overall
: comparisons.
超出平均的出局數(plays above average)的計算方法是先找到全聯盟的平均防守區域
評價(ZR)，乘以防守機會(Chances)，再防守員拿到全部的出局數比較。為了舉例的目的，
這裡所用的是列出的這群防守機會次數達到標準的防守球員的資料計算其平均數，而不是
用真正全聯盟的平均數。而且以作者的意見而言，更正確的數值應該就像Chris Dial用的,
應分為美國聯盟和國家聯盟分別的平均數值，而非全聯盟的平均值，因為一些因素(諸如投
手打擊)的影響應該分別計算更為準確。
: Now, let's try this again, treating balls outside of zone separately, so that
: we correctly reward both reliable fielders in their zone and players who make
: more plays outside of their zone. I will find the league average using only
: BIZ and Plays, and then do a separate calculation for balls outside of zone:
現在，我們再重新計算一次，將防守區域外的出局數(balls outside of zone)分開計
算，如此我們可以對野手在他的防守區域內的判斷能力(可靠度)，及防守區域外的防守範
圍，都可以給予正確的獎勵。
: Plays
: Above
: Name AVG Reliability Range New Total
: A. Everett 28 26 10 36
: O. Vizquel 14 16 -9 7
: J. Reyes 11 12 -6 6
: C. Barmes 11 9 11 20
: J. Bartlett 10 11 -11 0
: A. Gonzalez 9 8 8 16
: E. Renteria 7 6 8 14
: D. Eckstein 5 5 2 7
: J. Uribe 5 5 -2 3
: K. Greene 2 2 0 2
: R. Cedeno 1 -1 13 12
: J. Rollins 0 1 -7 -5
: J. Wilson -1 -1 -3 -4
: M. Young -3 -3 -5 -8
: B. Hall -4 -8 29 20
: C. Guillen -5 -5 -3 -7
: R. Furcal -6 -6 -1 -7
: Y. Betancourt -6 -7 4 -3
: M. Tejada -8 -7 -6 -13
: D. Jeter -11 -7 -21 -29
: H. Ramirez -11 -13 14 1
: A. Berroa -16 -14 -10 -25
: J. Peralta -16 -14 -12 -27
: O. Cabrera -17 -16 -1 -17
: We can compare the player’s OOZ plays to the average OOZ plays based on how
: many balls were hit in their zone. This is similar to what David Gassko and
: Chris Constancio did for defensive ratings in the Hardball Times Season
: Preview. For this to work we have to assume that the number of out-of-zone
: opportunities for players are proportional to their in zone opportunities.
: This may or may not be a good assumption. An alternative would be to use
: total ground balls as the denominator. A better way would be to create a
: measure of out of zone opportunities. For a shortstop we could take every
: groundball hit to the left of the third baseman or to the right of the second
: baseman, and subtract the ones already counted in the SS zone. This measure
: is not available, so for now I think using BIZ as an estimate is acceptable.
: “Reliability” is a measure using only balls in zone. For this group of
: shortstops, the average Zone Rating was .825. This group also made .1274
: plays out of zone for every ball hit into the zone. “Range” compares the
: player’s out of zone plays made to this average, and the new total is simply
: Range + Reliability.
我們可以比較防守球員在防守區域外(OOZ)的出局數和平均的防守區域外的出局數(用
打入他防守區域內的球為比例算出平均出局數)。這結果就像David Gassko和Chris
Constancio在Hardball Times Season上所作的防守評價。為了算出結果我們必須假定防守
區域外的防守機會是和防守區域內的防守區域是成比例關係的。這可能是或可能不是一個
好的假設。另外一種方法則是用全部的滾地球為分母。更好的方法則是記錄防守區域外的
防守機會。對一個游擊手而言，我們可以計算球打到三壘手的左邊或打到二壘手的右邊的
滾地球，再減掉已經計算打到游擊區的滾地球，就得到防守區域外的防守機會。但此一值
目前尚無法取得，所以目前用防守區域內(BIZ)的防守機會為比例去估計應該是可以接受。
"可靠度"(Reliability)是評估打到防守區域內的防守能力。"範圍"(Range)則比較防守員
在防守員在防守區域外取得出局數與平值值的差異，新的總合值(new total)則只是將
"可靠度"和"範圍"相加。
: The Highlights:
: Jason Bartlett did very well in Zone Rating but made very few plays outside
: his zone. In the end, he’s just an average shortstop.
: Bill Hall at the first step look a little below average, but made a
: tremendous number of plays outside his zone. This year he is being moved from
: shortstop to center field, but this may be a mistake as he makes many more
: plays than the average shortstop.
: Derek Jeter looks a little below average at first, but he’s even worse than
: that. Jeter has very limited range. Only Bartlett made fewer plays outside
: the zone, but Jeter played almost 50% more innings than Bartlett.
: Hanley Ramirez looks below average at first, tied with Jeter, but made a
: great number of plays out of his zone. He’s actually average or slightly
: above.
: Adam Everett already ranked far above any other shortstop in the game, but in
: addition to fielding everything hit near him he has excellent range as well.
: He may be the best defensive shortstop since Ozzie Smith.
重點的游擊手:
Jason Bartlett在防守區域評價的值相當漂亮，但在防守區域外拿到很少的出局數。最後
他只是一個平均水準的游擊手。
Bill Hall一開始看起來是個有點低於平均值的游擊手，但卻在防守區域外拿到相當多數目
的出局數。今年他正由游擊手的位置被移到中外野手，但這可能是個錯誤的決定，因為他
實際上比平均水準的游擊手拿到超出相當多的出局數。
Derek Jeter最初看是個稍微低於平均水準的游擊手，但是實際上是更糟。Jeter的防守範
圍相當有限。只有Bartlett比他在防守區域外拿到更少的出局數，但是Jeter防守的局數
比Bartlett多出50%(換言之Bartlett是小樣本，Jeter的值更準確)。
Hanley Ramirez最初看來也低於平均值，和Jeter差不多，但是他在防守區域外拿到很多的
出局數。他實際上是平均水準或有一些高出平均水準的游擊手。
Adam Everett已經排名高於所有的游擊手，但注意的是他不僅防守區域內相當可靠，防守
範圍也相當的大。他可以說是自Ozzie Smith之後最好的游擊手。