Question 974212
That's the percentage of area between the two green lines below:

{{{drawing(400,200,-5,5,-.5,1.5, graph(400,200,-5,5,-.5,1.5, exp(-x^2/2)), 

green(line(-1,0,-1,exp(-(-1)^2/2)),line(1,0,1,exp(-1^2/2))),locate(4.8,-.01,z),locate(4.8,.2,z)
  
)}}}


The percentage is 68.26894809%.  We know this because it has been calculated
by higher mathematics.

Edwin</pre>