Year | Number of Attacks1 | Percent | Mean | Variance | Standard Deviation | Coefficient of Variation |
2007 | 1 | 4.00% | 2.5 | 2.25 | 1.50 | 0.60 |
2008 | 7 | 28.00% | 20.25 | 4.50 | 1.80 | |
2009 | 3 | 12.00% | 0.25 | 0.50 | 0.20 | |
2010 | 0 | 0.00% | 6.25 | 2.50 | 1.00 | |
2011 | 2 | 8.00% | 0.25 | 0.50 | 0.20 | |
2012 | 2 | 8.00% | 0.25 | 0.50 | 0.20 | |
2013 | 1 | 4.00% | 2.25 | 1.50 | 0.60 | |
2014 | 4 | 16.00% | 2.25 | 1.50 | 0.60 | |
2015 | 2 | 8.00% | 0.25 | 0.50 | 0.20 | |
2016 | 3 | 12.00% | 0.25 | 0.50 | 0.20 | |
Sum | 25 |
| Average | 3.45 | 1.86 | 0.74 |