Question 621443
  <pre><font face = "Tohoma" size = 3 color = "indigo"><b> 
Hi,
Note:  Bell shaped Curve showing placement of z = 0, z = ±1, 2, 3 
Left or Right of z = 0 being 50% of the area under the standard normal curve...
{{{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))),green(line(2,0,2,exp(-2^2/2)),line(-2,0,-2,exp(-2^2/2))),green(line(3,0,3,exp(-3^2/2)),line(-3,0,-3,exp(-3^2/2))),green(line( 0,0, 0,exp(0^2/2))),locate(4.8,-.01,z),locate(4.8,.2,z))}}}
As to A set of data is normally distributed with a mean of 70 and SD of 4. <span style="text-decoration: overline">X</span> = 68 
 z = (68-70)/4 ={{{ -.5}}}
Exel function NORMSDIST(-.5) = .3085 , 30.85% to the left and 69.15% to the right
{{{drawing(400,200,-5,5,-.5,1.5, graph(400,200,-5,5,-.5,1.5, 0,exp(-x^2/2)), blue(line( -.5,0, -.5,exp(-.5^2/2))),locate(4.8,-.01,z),locate(4.8,.2,z))}}}