Engineering Tables/Normal Distribution/Tail Function Graph

The tail function is the area under the normal distribution N(0,1) between x and +∞:
 * $$\mbox{T}(x) = \int\limits_x^\infty {{1 \over {\sqrt {2\pi } }}\exp \left( { - {{y^2 } \over 2}} \right)dy} $$



For x > 6.5, the tail function can be approximated as:
 * $$\mbox{T}(x) = {1 \over {x\sqrt { 2\pi } }}\exp \left( { - {{x^2 } \over 2}} \right) $$