Investigation Chapter 2: Does the LA Galaxy Have a Home Field Advantage? Amanda Adams Statistical Reasoning in Sports Period One October 5, 2013
Does the LA Galaxy Have A Home Field Advantage? 2 Table of Contents Introduction...3 Two Way Table...5 Bar Chart...5 Segmented Bar Chart...6 Applet Simulation...7 Dot Plot...8 Conclusion...9 Works Cited...11 Investigation Guide Chapter 2...12 Investigation Checklist Chapter 2...13 Investigation Rubric Chapter 2...14
Does the LA Galaxy Have A Home Field Advantage? 3 Introduction For 6 years, the Los Angeles Galaxy boasted one of Soccer s most famous, most loved athletes: David Beckham; but this season was their first after losing him to his European roots and subsequent retirement. American soccer has not typically been revered as of the highest quality, compared to its southern neighbors, and especially not to the European competition. European soccer has a following in Europe that can be likened to the same or even more than Americans and football. The packed stadiums of English soccer and the tens of thousands of german soccer fans that come out to support Dortmund each week can hardly compare to the half filled stadiums and one section wide fan clubs of the LA Galaxy, but does that lack of the same type of home field atmosphere keep the Galaxy from having a home field advantage? For this investigation, I got the Galaxy s home and away stats from us.soccerway.com. I chose to analyze the 2013 MLS Regular season because it is the most recent, and after many changes to their team I feel like it is the most accurate season to draw from moving forward. Although they had 30 games this season, 6 were ties and rather than including them as some other statistic I just did not include them, especially because they had the same amount of ties at home and away, I determined the information unhelpful to investigating a home field advantage. The Galaxy is currently in 5 th place in the western conference of MLS, 30 games into a 34 game season. They have 46 goals for (26 home and 20 away) and 37 goals against (8 home and 29 away). Looking purely at these stats, it would appear that in winning percentages there is a definite home field advantage (51%) and the goals given up percentage also reflect a home field advantage (57%). I, however, chose not to analyze their performance based on goals against at home and away, because I feel that the goals against
Does the LA Galaxy Have A Home Field Advantage? 4 reflects mainly the defense s specific game performance and goals against reflects the offense s specific game performance, while the actual winning percentage better reflects the team as whole and how they perform together. They hypotheses I will be testing in this investigation are as follows: Null Hypothesis: The 2013 LA Galaxy has the same ability to win games at home and away. Alternate Hypothesis: The 2013 LA Galaxy has a greater ability to win games at home than away.
Does the LA Galaxy Have A Home Field Advantage? 5 Two Way Table Home Away Total Wins 9 4 13 Losses 2 9 11 Total 11 13 24 The two way table displays the information for the LA Galaxy s 2013 Season. It appears as though they performed better at home in the Home Depot Center, gathering a total of 9 wins at home and only 4 wins away. Their overall record was 13-11. Bar Chart 100% 2013 LA Galaxy Winning Percentage Home and Away 80% 60% 40% 81.818% 69.231% Home Away 20% 0% Wins 30.769% 18.182% Losses The Bar chart displays the Season Win and loss records for the LA Galaxy. This Graph shows a large disparity between wins at home and away. The difference is a remarkable 63.6%. This initially leads fans to believe that the Galaxy does have a Home Field Advantage.
Does the LA Galaxy Have A Home Field Advantage? 6 Segmented Bar Chart 100% 80% 2013 LA Galaxy Winning Percentage Home and Away 30.769% 60% 40% 81.818% 69.231% Losses Wins 20% 0% Home 18.182% Away The Segmented bar chart again displays the large difference between the LA Galaxy s home performance and on the road performance. Even though the team had more away games than home (13 versus 11) they still managed to win the same amount of games at home as they lost away. From the Bar Charts alone, it would appear that they do have a greater ability to win at home than away.
Does the LA Galaxy Have A Home Field Advantage? 7 Applet Simulation For the Applet simulation, the data required is the number of successes and failures in each context, the applet computes the success percentage in each context and produces the test statistic for you. It then simulates the same circumstances as many times as you wish. Steps for note card simulation: 1. Start with 24 equally sized note cards. 2. Label 13 of the cards with a w for win and 11 of them with an L for Loss. 3.Shuffle the cards and deal them into two piles, one with 11 cards to represent home games, and the other with 13 cards to represent the away games. 4. calculate the winning percentage of each pile and subtract the home winning percentage from the away wining percentage so that the value is comparable to the test statistic 5. plot the difference on a dot plot. 6. Repeat 100 times for accuracy. Test Statistic: Home Winning Percentage: 9/11 = 81.818% Away winning percentage: 4/13: 30.769% Test statistic (Home-Away): 81.818%-30.769%=51.049%
Does the LA Galaxy Have A Home Field Advantage? 8 Simulation Dot Plot Simulated Difference in Winning Percentage at Home and Away 35 30 25 20 15 10 5 0-60% -40% -20% 0% 20% 40% 60% Simulated Difference in Winning Percentages (Home-Away) The Dot plot shows the simulated values of the difference in winning percentages at home versus away. The results indicated that a difference of 51.049% will happen 1% of the time if the LA Galaxy has the same ability to win games at home and away. This gives the simulation a p-value of 0.01.
Does the LA Galaxy Have A Home Field Advantage? 9 Conclusion The simulation provided very convincing evidence of a greater ability to win games at home rather than away. The p-value of the simulation was 0.01, meaning that if we assume that the galaxy has the same ability to win games at home and away, a difference in ability in the two contexts will only occur once for every 100 sets of 24 games, so once every 100 seasons. Put into this perspective, it is easy to understand why this evidence is so convincing. Because the P-value is so small, and we have the convincing evidence, we reject the null hypothesis and support the alternative that the LA Galaxy has a greater ability to win at home than on the road. Although this was not an experiment, and we cannot make any assertions about the reason to their greater ability to win at home, we can speculate. Some contributors to the increased ability could be that the team has some pregame rituals that put them into a better mindset than when they travel. It could be that they sleep better in their own beds before a big game rather than a hotel. I have already addressed the fan situation, however; even with the limited amount of American soccer fans, it could be a factor for the Galaxy when playing in the Home Depot Center. Other factors could be that southern California has better weather than other places, that the players are more accustomed to their own field, or even something as insignificant that they like their home uniforms better. On the other side of the ethical coin, home refs could be biased towards their team. There is an endless possibility of explanations for the increased ability at home. Some errors in calculations could have occurred in the course of the investigation primarily because of the small amount of data. Because I was analyzing just one season of the Galaxy s performance, the disparity in winning percentages could just be because of the small sample size. To better answer the
Does the LA Galaxy Have A Home Field Advantage? 10 question: Does the LA Galaxy have a Home Field Advantage? a larger amount of games played would have given a more accurate picture of the Galaxy s performance. I, however, chose not to use more data than just the previous season because I believe that without David Beckham, the team is entirely new, not only because they lost a key player, but because he was also a captain and along with losing captain could mean losing certain aspects of a team dynamic. Losing any player changes a team, which is why I believe using only the immediate season s statistics were accurate.
Does the LA Galaxy Have A Home Field Advantage? 11 Works Cited "Statistical Reasoning in Sports." Statistical Reasoning in Sports. W H Freeman & Company, n.d. Web. 1 Oct. 2013. SoccerWay. Chart. Global Sports Media, n.d. Web. 1 Oct. 2013. "LA Galaxy." LA Galaxy. MLS, 2011. Web. 06 Oct. 2013.