Monday, July 1, 2019

Yards per carry and the NFL Draft

This post displays the potential importance of outliers.

Question Two:  How does the average of yards per carry for the first-choice running back differ from the average yards per carry for the second-choice running back?   How do the median, standard deviation, and skew of yards per carry for the first and second choice running backs differ?

Data:   The data used for this post can be found at

I originally collected the data at an NFL Web site.


Information on career yards per carry for first-choice and second-choice running backs is displayed in the table below.

First-Choice Running Back
Second-Choice Running Back
Average of years per carry
Median of yards per carry
Standard deviation of yards
 per carry
Skew of yards per carry

The average of yards per carry over the 33 draft years is slightly higher for second-choice running backs than for first-choice running backs.

The median of yards per carry is slightly larger for first-choice quarterbacks than for second choice quarterbacks.  

The standard deviation of yards per carry is over 3 times larger for first-choice running backs than for second-choice running backs.

The skew of first-choice running backs is highly negative indicating the existence of some very small observations.  The skew of the second-choice running back sample is 0.12 indicating the data is basically symmetrically distributed around the mean.


How can we explain these relatively strange results?    Larry Stegent the first-choice running back in 1970 blew out his knee in his first pre-season game.  He was included in our sample despite having zero yards.  He is an outlier.  Perhaps I should have excluded him from the sample.

Interested readers might want to compare the yards per carry statistics presented here to total career yards statistics discussed in a previous post.

#NFL Draft



No comments:

Post a Comment