## Friday, June 13, 2014

### 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 3.91 3.99 Median of yards per carry 4.10 4.00 Standard deviation of yards  per carry 0.80 0.25 Skew of yards per carry -3.77 0.12

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.

Discussion:

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.

http://en.wikipedia.org/wiki/Larry_Stegent

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

http://dailymathproblem.blogspot.com/2014/06/running-back-career-yardage-statistics.html

#NFL Draft

#NFL

#outliers