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April 16, 2014 6:00 am

Fantasy Freestyle: Fighting Early-Season Confirmation Bias

4

Jeff Quinton

Advice to help you avoid being steered off course by April results.

The 2014 season is not even 20 games old, but we are already at the height of confirmation bias season. After spending the offseason (or some portion of the offseason) analyzing players for the upcoming season, and after acting on that research and analysis in offseason trades and in our drafts and auctions, we have a strong desire to see a return on the time and effort invested, to see our decisions pan out.

Obviously, it is too early in the season for there to be much, if any, information to actually confirm or disconfirm our assumptions. There really is no short-term risk in seeking this confirmation bias; rather, the danger lies in how seeking confirming information will impact our future decisions. If we continue to ignore information that disconfirms our beliefs (player A is bad because of X), while seeking out information that confirms our beliefs (player X is good because of Y), we will tend to overvalue our players. The more we overvalue our players, the less we will look for opportunities to improve our team and the greater the chances of us passing up or missing opportunities to improve our team. By knowing how we allow ourselves to fall victim to confirmation bias (traps) and with a few tips on how to fight those instincts (solutions), we can free ourselves, at least a little bit, from the downsides of confirmation bias.

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September 24, 2013 8:46 am

Overthinking It: The Season in Small-Sample Narratives

7

Ben Lindbergh

A retrospective on the flashes in pans that briefly became big stories in 2013.

There’s only one thing as embarrassing as old yearbook photos: narratives from the start of the baseball season, as viewed from September. So much has happened since those first few months that it’s not always easy to remember what we were worried and excited about, even when we’re not actively trying to forget. Some early slumps and hot streaks are signs of things to come, but in retrospect, others seem impossibly quaint, like relics from a more ignorant age. With the regular season in its waning days, let’s look back at some of the flashes in pans that briefly became big stories.

Jarrod Parker needs a trip to Triple-A
Parker was awful in April. More accurately, he was awful in four of his six April starts, but those four were ugly enough to completely kayo his line. At the end of the month, he had a 7.36 ERA, which Bob Melvin called “puzzling” and columnists (after all of three outings) called grounds to propose putting him in the bullpen or sending him to Sacramento. Some of the right-hander’s struggles may have been bad luck—he had a .382 BABIP—but most likely he was suffering from some mechanical issues: Parker walked 16 in 29 1/3 April innings.


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Russell reruns the numbers to determine when hitter stats stabilize.

Who said sabermetrics hasn't gone mainstream? We've now reached the point where even mainstream analysts are yelling "small sample size!" at one another. There's always been some understanding that a player who goes 4-for-5 in a game is not really an .800 hitter, but now, people are being more explicit in talking about sample size. I consider that a victory. Hooray for sabermetrics!

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Nick Johnson: hitless in April, hero in May (plus .400 OBP update).

Presented without (much) comment: Nick Johnson's monthly splits so far this season.

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Great small-sample seasons might not be the most valuable, but they're often among the most entertaining.

Believe it or not, most of our writers didn't enter the world sporting an @baseballprospectus.com address; with a few exceptions, they started out somewhere else. In an effort to up your reading pleasure while tipping our caps to some of the most illuminating work being done elsewhere on the internet, we'll be yielding the stage once a week to the best and brightest baseball writers, researchers and thinkers from outside of the BP umbrella. If you'd like to nominate a guest contributor (including yourself), please drop us a line.

Chad Finn writes the Touching All The Bases blog for Boston.com and is the sports media columnist for The Boston Globe. He believes that Butch Hobson was actually a fine defensive third baseman, misses watching Pedro Martinez pitch, and would appreciate it if you gave him all of your good book ideas. He lives in Wells, Maine, with his wife, two children, and cat named after Otis Nixon.
 


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April 23, 2012 3:00 am

Pebble Hunting: Cautiously Sizing Up April Stats

4

Sam Miller

It's too early to look at statistical leaderboards, but sometimes we have to anyway.

April 19, 2011: "Somehow, someway, Carlos Lee is second with a 53.2 UZR/150. I will literally eat broken glass if he finishes with a positive number this season. (Someone hold me to it.)" —This guy, who is now dead, from eating glass :(

We have such a weird relationship with April stats. I’m trying to think of anything else where we consider a 10-percent sample almost totally useless. On election night, when they show the vote totals, I start to take them seriously once 10 percent of precincts are in. If you could see only 10 percent of a human, you could still probably figure out whether he was tall, fat, into rockabilly, etc. But the first 10 percent of a baseball season is like the first 10 percent of the sausage race in Milwaukee: filled with narrative, almost entirely misleading, and a place where Randall Simon doesn’t belong.

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We've said it before, and we'll say it again: it's best not to get too worked up over the first week's worth of action.

While looking toward the future with our comprehensive slate of current content, we'd also like to recognize our rich past by drawing upon our extensive (and mostly free) online archive of work dating back to 1997. In an effort to highlight the best of what's gone before, we'll be bringing you a weekly blast from BP's past, introducing or re-introducing you to some of the most informative and entertaining authors who have passed through our virtual halls. If you have fond recollections of a BP piece that you'd like to nominate for re-exposure to a wider audiencesend us your suggestion.

Before you read too much into early-season stats, take another look at Joe's warning about small sample size, which originally ran as a "Prospectus Today" column on April 13, 2009.
 


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April 12, 2012 4:32 am

Heartburn Hardball: The Dangers of First Impressions

0

Jonathan Bernhardt

A few young starters have dazzled us early, but some similar starts last season proved to be false ones.

A pitcher's first start of the year often seems like a momentous event. It's not the first time most fans will have seen him in the past month, but it is the first time his performance will count for anything more than tea leaves. For young pitchers, especially, the first start sets the bar for the expectations game fans and media types like to play with young and unproven players.

With the plodding morass of spring training behind us, our interest in Real Baseball reaches rabid heights for the first week or two of the season, before we settle into the jogger's pace that takes us to the All-Star break. However, the increased importance we assign to early-season starts doesn't make them reliable barometers. They're certainly no more worthy of consideration than any other individual start over the course of the season just because they're the only data point available at the end of the first week. So before we write too many more breathless words about Jake Arrieta, Jeff Samardzija, and others, let's revisit the good first impressions some young starters made last season and look at how things ended up for them.

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A's prospect Michael Choice is having quite the AFL season, but what can his success tell us about how stats should be presented?

Believe it or not, most of our writers didn't enter the world sporting an @baseballprospectus.com address; with a few exceptions, they started out somewhere else. In an effort to up your reading pleasure while tipping our caps to some of the most illuminating work being done elsewhere on the internet, we'll be yielding the stage once a week to the best and brightest baseball writers, researchers and thinkers from outside of the BP umbrella. If you'd like to nominate a guest contributor (including yourself), please drop us a line.

Matt Lentzner has carved out a (very) small niche in the baseball analysis world by examining the intersection of physics and biomechanics. He has presented at the PITCHf/x conference in each of the last two years and has written articles for The Hardball Times, as well as a previous articles for Baseball Prospectus. When he’s not writing, Matt works on his physics-based baseball simulator, which is so awesome and all-encompassing that it will likely never actually be finished, though it does provide the inspiration for most of his articles and presentations. In real life, he’s an IT Director at a small financial consulting company in the Silicon Valley and also runs a physical training gym in his backyard on the weekends.

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When is hot truly hot, and when is it not?

A few weeks ago, during the division series, Brandon McCarthy remarked on Twitter that it would be more interesting for TBS to show a diagram of the batter hot and cold zones for every batter than to show the PitchTrax strike zone and pitch location graphic. He argued that knowledge of the hot and cold zones would give viewers additional insight into the battle between the pitcher and the batter.

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Examining umpire calling and catcher framing leads to thought-provoking questions about the amorphous nature of the strike zone.

Ever since the PITCHf/x system debuted in the 2006 playoffs, people have been interested in what it says about the strike zone that the umpires call.

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More research is needed before we can truly know the effects of sleep on player performance.

Last week, we talked about the effects of sleep (or lack thereof) on a player’s performance, and it was all nice and theoretical, and at the end, I mumbled something about how a brilliant researcher might, in the future, be able to come up with some way to quantify these sorts of things. Welcome to the future. (See what I did there?)

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