By: Seth Friedman, Joseph Newman, Xiongfei Gao
Seth Friedman, Xiongfei Gao, Joseph Newman
In recent years, it has been claimed that the offensive production and statistics in the NFL have changed considerably. Articles such as this one that suggest the NFL is becoming a “passing league” are becoming more and more frequent. Many football analysts stress that having a franchise quarterback is more important than relying on a running back or defense, because that’s the way the league is now. The question to be asked, however, is: is it just the number of passing yards that have been increasing over the years, or is this a general trend across all of the offensive statistics?
In order to examine this, it would be helpful to examine a database containing the offensive statistics for the past couple of decades. To do this, we will be using the NFL.com statistics database and viewing the offensive data from 1966 (the year of the first Superbowl) to 2011. We will be analyzing both the number of passing yards/game and number of rushing yards/game to determine whether one has increased, both have increased, or none have increased. We are using the number of yards/game instead of just number of yards because the NFL season was changed from 14 to 16 games in 1977. For each statistic (i.e. passing or rushing), we will perform two one-tailed hypothesis tests (each using the median year of 1988 in the null hypothesis): one will test if the pre-1988 data is less than the 1988 average, and the other will test if the post-1988 data is greater than the 1988 average.
To do this, we will use μ = the 1988 average (219.4 for passing and 69.0 for rushing) for the null hypothesis for both one-tailed tests, and we will use μ < the 1988 average for the pre-1988 test’s alternate hypothesis and μ > the 1988 average for the post-1988 test’s alternate hypothesis. If we reject the null hypothesis, then it confirms that there is an increasing trend in the data, and if we fail to reject the null hypothesis, then we fail to show that there is an increasing trend. We will be examining the top 20 NFL quarterbacks and running backs instead of all of them, as this will not only still produce an accurate test result for each one-tailed test (20 players * approximately 20 years for each of the two tests equals around 400 data points to use, meaning that the Central Limit Theorem applies).
Other methods that we will be using for examining the data will include building a 95% confidence interval around the data, and we can also construct a couple of linear plots to confirm our conclusions about the statistics. For example, we can plot the number of passing yards/game versus the year, the number of rushing yards/game versus the year, and the number of rushing yards/game versus the number of passing yards/game. In all of these plots, we can use the tools that we have learned in class to determine whether or not a linear relationship exists between each of these sets of variables. Through all of this, we believe that we can definitively determine whether the offensive style of play has changed.
Jason Clary. (2011, June 09). NFL: Has the NFL really turned into a pass-first league?
Retrieved from: http://bleacherreport.com/articles/729496-nfl-has-the-nfl-really-turned-into -a-pass-first-league
NFL Statistics. http://www.nfl.com/stats/player