Use correct confidence interval

See table here: https://journals.plos.org/plosone/article/figure?id=10.1371/journal.pone.0118537.t001

Author: liamtoney

examples/statistics/confidence_ellipse.py

@@ -36,7 +36,7 @@
 # of standard deviations. The default value is 3 which makes the ellipse
 # enclose 99.4% of the points if the data is normally distributed
 # like in these examples (3 standard deviations in 1-D contain 99.7%
-# of the data, which is 99.4% of the data in 2-D).
+# of the data, which is 98.9% of the data in 2-D).
 
 
 def confidence_ellipse(x, y, ax, n_std=3.0, facecolor='none', **kwargs):